https://hades.mech.northwestern.edu//api.php?action=feedcontributions&feedformat=atom&user=NathanHenry 2026-05-19T10:32:58Z User contributions MediaWiki 1.43.8 https://hades.mech.northwestern.edu//index.php?title=Laser_cutter&diff=13052 2009-04-08T20:15:26Z

<p>NathanHenry: </p> <hr /> <div>[[Image:laser_cutter_pic|thumb|right|250px|Laser Cutter]]<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> ==Overview==<br /> [[Image:laser_cutter_cutting_pic|thumb|right|250px|Laser Cutter Cutting]]<br /> The laser cutter, available in the prototyping lab, is an extremely useful tool for quickly cutting 2-D plastic parts. The machine uses a high intensity IR laser to cut any two dimensional design out of a plastic sheet. Acrylic is by far the best material for use with the laser cutter; when acrylic is used, the tool is capable of cutting through up to a 1/2&quot; thick piece.<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> The laser can be used for both cutting and etching; if the intensity is low, or the piece is thick it will only cut part way through the sheet in one pass.<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> '''If you are using a plastic other than acrylic, consult with the shop staff before cutting.'''<br /> &lt;br&gt;<br /> '''If you have never used the laser cutter before, ask for help if you encounter any problems. '''<br /> &lt;br clear=all&gt;<br /> <br /> ==Creating and Importing a File==<br /> To print to the laser cutter, a drawing must be prepared in CorelDRAW and placed on the laser cutter template, found on the desktop of the laser cutter computer. Drawing simple shapes, such as squares and circles is easy in CorelDRAW, however, for most applications with more advanced geometry it is better to use a more sophisticated CAD program. To transport the geometry from a solid modeler, such as Unigraphics, the part must be saved in a two-dimensional format, such as .dxf or .dwg. The drawing can then be imported into CorelDRAW and printed.<br /> ===Creating a .DXF or .DWG===<br /> The part must first be designed in a CAD system. If using AutoCAD, the part will automatically be saved in a .dwg format. However, if you are using a solid modeler, such as UG or SolidWorks, the part will be saved as a .prt. To convert a three dimensional piece, to a two-dimensional drawing in .dxf or .dwg format, simply go to Save As ... and select the appropriate extension. This file can now be imported into CorelDRAW, where it can be printed.<br /> ===Importing Files===<br /> To import the file, first open the Laser Cutter Template, found on the desktop. This is a canvass, the same size as the laser cutter's cutting area, which is used to lay out the drawing or drawings for printing. To add a .dxf or .dwg, simply gp to File -&gt; Import and select the correct extension and browse to you desired file. The drawing can then be placed anywhere on the template. The rulers on the template correspond exactly to the rulers on the laser cutter, so if your sheet of plastic is smaller than the cutting area of the laser cutter, be sure that the drawing lies entirely within the necessary dimensions. The sheet is normally placed in the top left corner, using the rulers as a square corner, so place your drawings here.<br /> <br /> ==Using the Laser Cutter==<br /> Once the drawing is loaded and ready to print, follow the instructions below. To turn the laser cutter on, press the orange power button on the right side of the machine in the back.<br /> ===Fumes Release Valve===<br /> Cutting some plastic releases toxic fumes. In order to prevent leaking these fumes into the air, the fumes release valve must be opened. This creates a vacuum, which sucks the toxic fumes out of the machine. The valve is yellow, and located above the machine on the left. Push down to open. To verify that the valve is open, check the pressure gauge. <br /> ===Setting the Laser Height===<br /> The laser must be set at a specific height (~1/8&quot; above the material) for the best results. There is a tool, located just to the left of the laser cutter bed, which is designed for this purpose. On the laser cutter control panel, select Z-height. This allows you to move the table up and down to the proper level. Place your material in the bed and the tool on top of the material as shown. Adjust the table so that the laser mounting aligns with the flat edge on the tool. The proper height is shown in the image. Once the height is correct, select exit.<br /> ===Printing to the Laser Cutter===<br /> You are now ready to print. From CorelDRAW, select file Print. The laser cutter will appear as the first printer listed. Select 'Properties' from the printer window to set the laser parameters. First, select the black from the list of colors. This allows you to set the laser speed and intensity. <br /> ====Selecting Speed====<br /> Set the speed anywhere from 25-50%. The slower the speed, the deeper the cut will be. If the first couple of passes does not complete cut through the plastic, try reducing the speed so that each cut is deeper. <br /> ====Selecting Intensity====<br /> For most cutting applications, 100% intensity is fine. However, if you are etching, less intensity might be desired.Consult the shop staff if you have questions regarding an appropriate intensity level.<br /> ====Printing====<br /> Once the speed and intensity are selected, press the large 'Set' button. Then exit the properties window and select print. This will send the document to the laser cutter. On the laser cutter screen, the document name will be displayed. If this is correct, press the green button to proceed. This will cause the laser to make the first pass. Multiple passes may be necessary to complete cut the plastic. Once the run is complete, simply repress the green button to start another pass. If you want to adjust the speed or intensity, you must reprint the document, with the new values, from the computer.</div>

NathanHenry https://hades.mech.northwestern.edu//index.php?title=Laser_cutter&diff=13051 2009-04-02T19:20:21Z

<p>NathanHenry: /* Overview */</p> <hr /> <div>[[Image:laser_cutter_pic|thumb|right|250px|Laser Cutter]]<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> ==Overview==<br /> [[Image:laser_cutter_cutting_pic|thumb|right|250px|Laser Cutter Cutting]]<br /> The laser cutter, available in the prototyping lab, is an extremely useful tool for quickly cutting 2-D plastic parts. The machine uses a high intensity IR laser to cut any two dimensional design out of a plastic sheet. Acrylic is by far the best material for use with the laser cutter; when acrylic is used, the tool is capable of cutting through up to a 1/2&quot; thick piece.<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> The laser can be used for both cutting and etching; if the intensity is low, or the piece is thick it will only cut part way through the sheet in one pass.<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> '''If you are using a plastic other than acrylic, consult with the shop staff before cutting.'''<br /> &lt;br&gt;<br /> '''If you have never used the laser cutter before, ask for help if you encounter any problems. '''<br /> &lt;br clear=all&gt;<br /> <br /> ==Creating and Importing a File==<br /> To print to the laser cutter, a drawing must be prepared in CorelDRAW and placed on the laser cutter template, found on the desktop of the laser cutter computer. Drawing simple shapes, such as squares and circles is easy in CorelDRAW, however, for most applications with more advanced geometry it is better to use a more sophisticated CAD program. To transport the geometry from a solid modeler, such as Unigraphics, the part must be saved in a two-dimensional format, such as .dxf or .dwg. The drawing can then be imported into CorelDRAW and printed.<br /> ===Creating a .DXF or .DWG===<br /> The part must first be designed in a CAD system. If using AutoCAD, the part will automatically be saved in a .dwg format. However, if you are using a solid modeler, such as UG or SolidWorks, the part will be saved as a .prt. To convert a three dimensional piece, to a two-dimensional drawing in .dxf or .dwg format, simply go to Save As ... and select the appropriate extension. This file can now be imported into CorelDRAW, where it can be printed.<br /> ===Importing Files===<br /> To import the file, first open the Laser Cutter Template, found on the desktop. This is a canvass, the same size as the laser cutter's cutting area, which is used to lay out the drawing or drawings for printing. To add a .dxf or .dwg, simply gp to File -&gt; Import and select the correct extension and browse to you desired file. The drawing can then be placed anywhere on the template. The rulers on the template correspond exactly to the rulers on the laser cutter, so if your sheet of plastic is smaller than the cutting area of the laser cutter, be sure that the drawing lies entirely within the necessary dimensions. The sheet is normally placed in the top left corner, using the rulers as a square corner, so place your drawings here.<br /> <br /> ==Using the Laser Cutter==<br /> ===Fumes Release Valve===<br /> ===Setting the Laser Height===<br /> ===Printing to the Laser Cutter===<br /> ====Selecting Speed====<br /> ====Selecting Intensity====<br /> ====Re-Printing====</div>

NathanHenry https://hades.mech.northwestern.edu//index.php?title=Laser_cutter&diff=13050 2009-04-02T19:19:27Z

<p>NathanHenry: /* Overview */</p> <hr /> <div>[[Image:laser_cutter_pic|thumb|right|250px|Laser Cutter]]<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> ==Overview==<br /> [[Image:laser_cutter_cutting_pic|thumb|right|250px|Laser Cutter Cutting]]<br /> The laser cutter, available in the prototyping lab, is an extremely useful tool for quickly cutting 2-D plastic parts. The machine uses a high intensity IR laser to cut any two dimensional design out of a plastic sheet. Acrylic is by far the best material for use with the laser cutter; when acrylic is used, the tool is capable of cutting through up to a 1/2&quot; thick piece.<br /> &lt;br&gt;<br /> The laser can be used for both cutting and etching; if the intensity is low, or the piece is thick it will only cut part way through the sheet in one pass.<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> '''If you are using a plastic other than acrylic, consult with the shop staff before cutting.'''<br /> &lt;br&gt;<br /> '''If you have never used the laser cutter before, ask for help if you encounter any problems. '''<br /> <br /> ==Creating and Importing a File==<br /> To print to the laser cutter, a drawing must be prepared in CorelDRAW and placed on the laser cutter template, found on the desktop of the laser cutter computer. Drawing simple shapes, such as squares and circles is easy in CorelDRAW, however, for most applications with more advanced geometry it is better to use a more sophisticated CAD program. To transport the geometry from a solid modeler, such as Unigraphics, the part must be saved in a two-dimensional format, such as .dxf or .dwg. The drawing can then be imported into CorelDRAW and printed.<br /> ===Creating a .DXF or .DWG===<br /> The part must first be designed in a CAD system. If using AutoCAD, the part will automatically be saved in a .dwg format. However, if you are using a solid modeler, such as UG or SolidWorks, the part will be saved as a .prt. To convert a three dimensional piece, to a two-dimensional drawing in .dxf or .dwg format, simply go to Save As ... and select the appropriate extension. This file can now be imported into CorelDRAW, where it can be printed.<br /> ===Importing Files===<br /> To import the file, first open the Laser Cutter Template, found on the desktop. This is a canvass, the same size as the laser cutter's cutting area, which is used to lay out the drawing or drawings for printing. To add a .dxf or .dwg, simply gp to File -&gt; Import and select the correct extension and browse to you desired file. The drawing can then be placed anywhere on the template. The rulers on the template correspond exactly to the rulers on the laser cutter, so if your sheet of plastic is smaller than the cutting area of the laser cutter, be sure that the drawing lies entirely within the necessary dimensions. The sheet is normally placed in the top left corner, using the rulers as a square corner, so place your drawings here.<br /> <br /> ==Using the Laser Cutter==<br /> ===Fumes Release Valve===<br /> ===Setting the Laser Height===<br /> ===Printing to the Laser Cutter===<br /> ====Selecting Speed====<br /> ====Selecting Intensity====<br /> ====Re-Printing====</div>

NathanHenry https://hades.mech.northwestern.edu//index.php?title=Laser_cutter&diff=13049 2009-04-02T19:17:38Z

<p>NathanHenry: /* Overview */</p> <hr /> <div>[[Image:laser_cutter_pic|thumb|right|250px|Laser Cutter]]<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> ==Overview==<br /> [[Image:laser_cutter_cutting_pic|thumb|right|250px|Laser Cutter Cutting]]<br /> The laser cutter, available in the prototyping lab, is an extremely useful tool for quickly cutting 2-D plastic parts. The machine uses a high intensity IR laser to cut any two dimensional design out of a plastic sheet. Acrylic is by far the best material for use with the laser cutter; when acrylic is used, the tool is capable of cutting through up to a 1/2&quot; thick piece.<br /> &lt;br&gt;<br /> The laser can be used for both cutting and etching; if the intensity is low, or the piece is thick it will only cut part way through in one pass.<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> '''If you are using a plastic other than acrylic, consult with the shop staff before cutting.'''<br /> &lt;br&gt;<br /> '''If you have never used the laser cutter before, ask for help if you encounter any problems. '''<br /> <br /> ==Creating and Importing a File==<br /> To print to the laser cutter, a drawing must be prepared in CorelDRAW and placed on the laser cutter template, found on the desktop of the laser cutter computer. Drawing simple shapes, such as squares and circles is easy in CorelDRAW, however, for most applications with more advanced geometry it is better to use a more sophisticated CAD program. To transport the geometry from a solid modeler, such as Unigraphics, the part must be saved in a two-dimensional format, such as .dxf or .dwg. The drawing can then be imported into CorelDRAW and printed.<br /> ===Creating a .DXF or .DWG===<br /> The part must first be designed in a CAD system. If using AutoCAD, the part will automatically be saved in a .dwg format. However, if you are using a solid modeler, such as UG or SolidWorks, the part will be saved as a .prt. To convert a three dimensional piece, to a two-dimensional drawing in .dxf or .dwg format, simply go to Save As ... and select the appropriate extension. This file can now be imported into CorelDRAW, where it can be printed.<br /> ===Importing Files===<br /> To import the file, first open the Laser Cutter Template, found on the desktop. This is a canvass, the same size as the laser cutter's cutting area, which is used to lay out the drawing or drawings for printing. To add a .dxf or .dwg, simply gp to File -&gt; Import and select the correct extension and browse to you desired file. The drawing can then be placed anywhere on the template. The rulers on the template correspond exactly to the rulers on the laser cutter, so if your sheet of plastic is smaller than the cutting area of the laser cutter, be sure that the drawing lies entirely within the necessary dimensions. The sheet is normally placed in the top left corner, using the rulers as a square corner, so place your drawings here.<br /> <br /> ==Using the Laser Cutter==<br /> ===Fumes Release Valve===<br /> ===Setting the Laser Height===<br /> ===Printing to the Laser Cutter===<br /> ====Selecting Speed====<br /> ====Selecting Intensity====<br /> ====Re-Printing====</div>

NathanHenry https://hades.mech.northwestern.edu//index.php?title=Laser_cutter&diff=13048 2009-04-02T19:11:44Z

<p>NathanHenry: </p> <hr /> <div>[[Image:laser_cutter_pic|thumb|right|250px|Laser Cutter]]<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> ==Overview==<br /> [[Image:laser_cutter_cutting_pic|thumb|right|250px|Laser Cutter Cutting]]<br /> The laser cutter, available in the prototyping lab, is an extremely useful tool for quickly cutting 2-D plastic parts. The machine uses a high intensity IR laser to cut any two dimensional design out of a plastic sheet. Acrylic is by far the best material for use with the laser cutter; when acrylic is used, the tool is capable of cutting through up to a 1/2&quot; thick piece.<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> '''If you are using a plastic other than acrylic, consult with the shop staff before cutting.'''<br /> &lt;br&gt;<br /> '''If you have never used the laser cutter before, ask for help if you encounter any problems. '''<br /> <br /> <br /> ==Creating and Importing a File==<br /> To print to the laser cutter, a drawing must be prepared in CorelDRAW and placed on the laser cutter template, found on the desktop of the laser cutter computer. Drawing simple shapes, such as squares and circles is easy in CorelDRAW, however, for most applications with more advanced geometry it is better to use a more sophisticated CAD program. To transport the geometry from a solid modeler, such as Unigraphics, the part must be saved in a two-dimensional format, such as .dxf or .dwg. The drawing can then be imported into CorelDRAW and printed.<br /> ===Creating a .DXF or .DWG===<br /> The part must first be designed in a CAD system. If using AutoCAD, the part will automatically be saved in a .dwg format. However, if you are using a solid modeler, such as UG or SolidWorks, the part will be saved as a .prt. To convert a three dimensional piece, to a two-dimensional drawing in .dxf or .dwg format, simply go to Save As ... and select the appropriate extension. This file can now be imported into CorelDRAW, where it can be printed.<br /> ===Importing Files===<br /> To import the file, first open the Laser Cutter Template, found on the desktop. This is a canvass, the same size as the laser cutter's cutting area, which is used to lay out the drawing or drawings for printing. To add a .dxf or .dwg, simply gp to File -&gt; Import and select the correct extension and browse to you desired file. The drawing can then be placed anywhere on the template. The rulers on the template correspond exactly to the rulers on the laser cutter, so if your sheet of plastic is smaller than the cutting area of the laser cutter, be sure that the drawing lies entirely within the necessary dimensions. The sheet is normally placed in the top left corner, using the rulers as a square corner, so place your drawings here.<br /> <br /> ==Using the Laser Cutter==<br /> ===Fumes Release Valve===<br /> ===Setting the Laser Height===<br /> ===Printing to the Laser Cutter===<br /> ====Selecting Speed====<br /> ====Selecting Intensity====<br /> ====Re-Printing====</div>

NathanHenry https://hades.mech.northwestern.edu//index.php?title=Laser_cutter&diff=13047 2009-04-02T19:11:21Z

<p>NathanHenry: </p> <hr /> <div>[[Image:laser_cutter_pic|thumb|right|250px|Laser Cutter]]<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> ==Overview==<br /> [[Image:laser_cutter_cutting_pic|thumb|right|250px|Laser Cutter Cutting]]<br /> The laser cutter, available in the prototyping lab, is an extremely useful tool for quickly cutting 2-D plastic parts. The machine uses a high intensity IR laser to cut any two dimensional design out of a plastic sheet. Acrylic is by far the best material for use with the laser cutter; when acrylic is used, the tool is capable of cutting through up to a 1/2&quot; thick piece.<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> '''If you are using a plastic other than acrylic, consult with the shop staff before cutting.'''<br /> &lt;br&gt;<br /> '''If you have never used the laser cutter before, ask for help if you encounter any problems. '''<br /> <br /> <br /> ==Creating and Importing a File==<br /> To print to the laser cutter, a drawing must be prepared in CorelDRAW and placed on the laser cutter template, found on the desktop of the laser cutter computer. Drawing simple shapes, such as squares and circles is easy in CorelDRAW, however, for most applications with more advanced geometry it is better to use a more sophisticated CAD program. To transport the geometry from a solid modeler, such as Unigraphics, the part must be saved in a two-dimensional format, such as .dxf or .dwg. The drawing can then be imported into CorelDRAW and printed.<br /> ===Creating a .DXF or .DWG===<br /> The part must first be designed in a CAD system. If using AutoCAD, the part will automatically be saved in a .dwg format. However, if you are using a solid modeler, such as UG or SolidWorks, the part will be saved as a .prt. To convert a three dimensional piece, to a two-dimensional drawing in .dxf or .dwg format, simply go to Save As ... and select the appropriate extension. This file can now be imported into CorelDRAW, where it can be printed.<br /> ===Importing Files===<br /> To import the file, first open the Laser Cutter Template, found on the desktop. This is a canvass, the same size as the laser cutter's cutting area, which is used to lay out the drawing or drawings for printing. To add a .dxf or .dwg, simply gp to File -&gt; Import and select the correct extension and browse to you desired file. The drawing can then be placed anywhere on the template. The rulers on the template correspond exactly to the rulers on the laser cutter, so if your sheet of plastic is smaller than the cutting area of the laser cutter, be sure that the drawing lies entirely within the necessary dimensions. The sheet is normally placed in the top left corner, using the rulers as a square corner, so place your drawings here.<br /> <br /> ==Using the Laser Cutter==<br /> ===Fumes Release Valve===<br /> ===Setting the Laser Height===<br /> ===Printing to the Laser Cutter===<br /> ====Selecting Speed====<br /> ====Selecting Intensity====<br /> ====Re-Printing====</div>

NathanHenry https://hades.mech.northwestern.edu//index.php?title=File:Laser_cutter_cutting_pic&diff=13046 2009-04-02T19:08:56Z

<p>NathanHenry: </p> <hr /> <div></div>

NathanHenry https://hades.mech.northwestern.edu//index.php?title=Laser_cutter&diff=13045 2009-04-02T19:08:31Z

<p>NathanHenry: </p> <hr /> <div>[[Image:laser_cutter_pic|thumb|right|250px|Laser Cutter]]<br /> &lt;br&gt;<br /> ==Overview==<br /> [[Image:laser_cutter_cutting_pic|thumb|right|250px|Laser Cutter Cutting]]<br /> The laser cutter, available in the prototyping lab, is an extremely useful tool for quickly cutting 2-D plastic parts. The machine uses a high intensity IR laser to cut any two dimensional design out of a plastic sheet. Acrylic is by far the best material for use with the laser cutter; when acrylic is used, the tool is capable of cutting through up to a 1/2&quot; thick piece.<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> '''If you are using a plastic other than acrylic, consult with the shop staff before cutting.'''<br /> &lt;br&gt;<br /> '''If you have never used the laser cutter before, ask for help if you encounter any problems. '''<br /> <br /> <br /> ==Creating and Importing a File==<br /> To print to the laser cutter, a drawing must be prepared in CorelDRAW and placed on the laser cutter template, found on the desktop of the laser cutter computer. Drawing simple shapes, such as squares and circles is easy in CorelDRAW, however, for most applications with more advanced geometry it is better to use a more sophisticated CAD program. To transport the geometry from a solid modeler, such as Unigraphics, the part must be saved in a two-dimensional format, such as .dxf or .dwg. The drawing can then be imported into CorelDRAW and printed.<br /> ===Creating a .DXF or .DWG===<br /> The part must first be designed in a CAD system. If using AutoCAD, the part will automatically be saved in a .dwg format. However, if you are using a solid modeler, such as UG or SolidWorks, the part will be saved as a .prt. To convert a three dimensional piece, to a two-dimensional drawing in .dxf or .dwg format, simply go to Save As ... and select the appropriate extension. This file can now be imported into CorelDRAW, where it can be printed.<br /> ===Importing Files===<br /> To import the file, first open the Laser Cutter Template, found on the desktop. This is a canvass, the same size as the laser cutter's cutting area, which is used to lay out the drawing or drawings for printing. To add a .dxf or .dwg, simply gp to File -&gt; Import and select the correct extension and browse to you desired file. The drawing can then be placed anywhere on the template. The rulers on the template correspond exactly to the rulers on the laser cutter, so if your sheet of plastic is smaller than the cutting area of the laser cutter, be sure that the drawing lies entirely within the necessary dimensions. The sheet is normally placed in the top left corner, using the rulers as a square corner, so place your drawings here.<br /> <br /> ==Using the Laser Cutter==<br /> ===Fumes Release Valve===<br /> ===Setting the Laser Height===<br /> ===Printing to the Laser Cutter===<br /> ====Selecting Speed====<br /> ====Selecting Intensity====<br /> ====Re-Printing====</div>

NathanHenry https://hades.mech.northwestern.edu//index.php?title=Laser_cutter&diff=13044 2009-04-02T19:05:19Z

<p>NathanHenry: </p> <hr /> <div>[[Image:laser_cutter_pic|thumb|right|250px|Laser Cutter]]<br /> &lt;br&gt;<br /> ==Overview==<br /> <br /> The laser cutter, available in the prototyping lab, is an extremely useful tool for quickly cutting 2-D plastic parts. The machine uses a high intensity IR laser to cut any two dimensional design out of a plastic sheet. Acrylic is by far the best material for use with the laser cutter; when acrylic is used, the tool is capable of cutting through up to a 1/2&quot; thick piece.<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> '''If you are using a plastic other than acrylic, consult with the shop staff before cutting.'''<br /> &lt;br&gt;<br /> '''If you have never used the laser cutter before, ask for help if you encounter any problems. '''<br /> <br /> <br /> ==Creating and Importing a File==<br /> To print to the laser cutter, a drawing must be prepared in CorelDRAW and placed on the laser cutter template, found on the desktop of the laser cutter computer. Drawing simple shapes, such as squares and circles is easy in CorelDRAW, however, for most applications with more advanced geometry it is better to use a more sophisticated CAD program. To transport the geometry from a solid modeler, such as Unigraphics, the part must be saved in a two-dimensional format, such as .dxf or .dwg. The drawing can then be imported into CorelDRAW and printed.<br /> ===Creating a .DXF or .DWG===<br /> The part must first be designed in a CAD system. If using AutoCAD, the part will automatically be saved in a .dwg format. However, if you are using a solid modeler, such as UG or SolidWorks, the part will be saved as a .prt. To convert a three dimensional piece, to a two-dimensional drawing in .dxf or .dwg format, simply go to Save As ... and select the appropriate extension. This file can now be imported into CorelDRAW, where it can be printed.<br /> ===Importing Files===<br /> To import the file, first open the Laser Cutter Template, found on the desktop. This is a canvass, the same size as the laser cutter's cutting area, which is used to lay out the drawing or drawings for printing. To add a .dxf or .dwg, simply gp to File -&gt; Import and select the correct extension and browse to you desired file. The drawing can then be placed anywhere on the template. The rulers on the template correspond exactly to the rulers on the laser cutter, so if your sheet of plastic is smaller than the cutting area of the laser cutter, be sure that the drawing lies entirely within the necessary dimensions. The sheet is normally placed in the top left corner, using the rulers as a square corner, so place your drawings here.<br /> <br /> ==Using the Laser Cutter==<br /> ===Fumes Release Valve===<br /> ===Setting the Laser Height===<br /> ===Printing to the Laser Cutter===<br /> ====Selecting Speed====<br /> ====Selecting Intensity====<br /> ====Re-Printing====</div>

NathanHenry https://hades.mech.northwestern.edu//index.php?title=Laser_cutter&diff=13043 2009-04-02T19:05:01Z

<p>NathanHenry: </p> <hr /> <div>[[Image:laser_cutter_pic|thumb|right|250px|Laser Cutter]]<br /> &lt;br clear=all&gt;<br /> ==Overview==<br /> <br /> The laser cutter, available in the prototyping lab, is an extremely useful tool for quickly cutting 2-D plastic parts. The machine uses a high intensity IR laser to cut any two dimensional design out of a plastic sheet. Acrylic is by far the best material for use with the laser cutter; when acrylic is used, the tool is capable of cutting through up to a 1/2&quot; thick piece.<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> '''If you are using a plastic other than acrylic, consult with the shop staff before cutting.'''<br /> &lt;br&gt;<br /> '''If you have never used the laser cutter before, ask for help if you encounter any problems. '''<br /> <br /> <br /> ==Creating and Importing a File==<br /> To print to the laser cutter, a drawing must be prepared in CorelDRAW and placed on the laser cutter template, found on the desktop of the laser cutter computer. Drawing simple shapes, such as squares and circles is easy in CorelDRAW, however, for most applications with more advanced geometry it is better to use a more sophisticated CAD program. To transport the geometry from a solid modeler, such as Unigraphics, the part must be saved in a two-dimensional format, such as .dxf or .dwg. The drawing can then be imported into CorelDRAW and printed.<br /> ===Creating a .DXF or .DWG===<br /> The part must first be designed in a CAD system. If using AutoCAD, the part will automatically be saved in a .dwg format. However, if you are using a solid modeler, such as UG or SolidWorks, the part will be saved as a .prt. To convert a three dimensional piece, to a two-dimensional drawing in .dxf or .dwg format, simply go to Save As ... and select the appropriate extension. This file can now be imported into CorelDRAW, where it can be printed.<br /> ===Importing Files===<br /> To import the file, first open the Laser Cutter Template, found on the desktop. This is a canvass, the same size as the laser cutter's cutting area, which is used to lay out the drawing or drawings for printing. To add a .dxf or .dwg, simply gp to File -&gt; Import and select the correct extension and browse to you desired file. The drawing can then be placed anywhere on the template. The rulers on the template correspond exactly to the rulers on the laser cutter, so if your sheet of plastic is smaller than the cutting area of the laser cutter, be sure that the drawing lies entirely within the necessary dimensions. The sheet is normally placed in the top left corner, using the rulers as a square corner, so place your drawings here.<br /> <br /> ==Using the Laser Cutter==<br /> ===Fumes Release Valve===<br /> ===Setting the Laser Height===<br /> ===Printing to the Laser Cutter===<br /> ====Selecting Speed====<br /> ====Selecting Intensity====<br /> ====Re-Printing====</div>

NathanHenry https://hades.mech.northwestern.edu//index.php?title=Laser_cutter&diff=13042 2009-04-02T19:04:12Z

<p>NathanHenry: </p> <hr /> <div>[[Image:laser_cutter_pic|thumb|right|250px|Laser Cutter]]<br /> ==Overview==<br /> <br /> The laser cutter, available in the prototyping lab, is an extremely useful tool for quickly cutting 2-D plastic parts. The machine uses a high intensity IR laser to cut any two dimensional design out of a plastic sheet. Acrylic is by far the best material for use with the laser cutter; when acrylic is used, the tool is capable of cutting through up to a 1/2&quot; thick piece.<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> '''If you are using a plastic other than acrylic, consult with the shop staff before cutting.'''<br /> &lt;br&gt;<br /> '''If you have never used the laser cutter before, ask for help if you encounter any problems. '''<br /> &lt;br clear=all&gt;<br /> <br /> ==Creating and Importing a File==<br /> To print to the laser cutter, a drawing must be prepared in CorelDRAW and placed on the laser cutter template, found on the desktop of the laser cutter computer. Drawing simple shapes, such as squares and circles is easy in CorelDRAW, however, for most applications with more advanced geometry it is better to use a more sophisticated CAD program. To transport the geometry from a solid modeler, such as Unigraphics, the part must be saved in a two-dimensional format, such as .dxf or .dwg. The drawing can then be imported into CorelDRAW and printed.<br /> ===Creating a .DXF or .DWG===<br /> The part must first be designed in a CAD system. If using AutoCAD, the part will automatically be saved in a .dwg format. However, if you are using a solid modeler, such as UG or SolidWorks, the part will be saved as a .prt. To convert a three dimensional piece, to a two-dimensional drawing in .dxf or .dwg format, simply go to Save As ... and select the appropriate extension. This file can now be imported into CorelDRAW, where it can be printed.<br /> ===Importing Files===<br /> To import the file, first open the Laser Cutter Template, found on the desktop. This is a canvass, the same size as the laser cutter's cutting area, which is used to lay out the drawing or drawings for printing. To add a .dxf or .dwg, simply gp to File -&gt; Import and select the correct extension and browse to you desired file. The drawing can then be placed anywhere on the template. The rulers on the template correspond exactly to the rulers on the laser cutter, so if your sheet of plastic is smaller than the cutting area of the laser cutter, be sure that the drawing lies entirely within the necessary dimensions. The sheet is normally placed in the top left corner, using the rulers as a square corner, so place your drawings here.<br /> <br /> ==Using the Laser Cutter==<br /> ===Fumes Release Valve===<br /> ===Setting the Laser Height===<br /> ===Printing to the Laser Cutter===<br /> ====Selecting Speed====<br /> ====Selecting Intensity====<br /> ====Re-Printing====</div>

NathanHenry https://hades.mech.northwestern.edu//index.php?title=Laser_cutter&diff=13041 2009-04-02T19:03:02Z

<p>NathanHenry: </p> <hr /> <div>[[Image:laser_cutter_pic|thumb|right|250px|Laser Cutter]]<br /> ==Overview==<br /> <br /> The laser cutter, available in the prototyping lab, is an extremely useful tool for quickly cutting 2-D plastic parts. The machine uses a high intensity IR laser to cut any two dimensional design out of a plastic sheet. Acrylic is by far the best material for use with the laser cutter; when acrylic is used, the tool is capable of cutting through up to a 1/2&quot; thick piece.<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> '''If you are using a plastic other than acrylic, consult with the shop staff before cutting.'''<br /> &lt;br&gt;<br /> '''If you have never used the laser cutter before, ask for help if you encounter any problems. '''<br /> &lt;br clear=all&gt;<br /> <br /> ==Creating and Importing a File==<br /> To print to the laser cutter, a drawing must be prepared in CorelDRAW and placed on the laser cutter template, found on the desktop of the laser cutter computer. Drawing simple shapes, such as squares and circles is easy in CorelDRAW, however, for most applications with more advanced geometry it is better to use a more sophisticated CAD program. To transport the geometry from a solid modeler, such as Unigraphics, the part must be saved in a two-dimensional format, such as .dxf or .dwg. The drawing can then be imported into CorelDRAW and printed.<br /> ===Creating a .DXF or .DWG===<br /> The part must first be designed in a CAD system. If using AutoCAD, the part will automatically be saved in a .dwg format. However, if you are using a solid modeler, such as UG or SolidWorks, the part will be saved as a .prt. To convert a three dimensional piece, to a two-dimensional drawing in .dxf or .dwg format, simply go to Save As ... and select the appropriate extension. This file can now be imported into CorelDRAW, where it can be printed.<br /> ===Importing Files===<br /> To import the file, first open the Laser Cutter Template, found on the desktop. This is a canvass, the same size as the laser cutter's cutting area, which is used to lay out the drawing or drawings for printing. To add a .dxf or .dwg, simply gp to File -&gt; Import and select the correct extension and browse to you desired file. The drawing can then be placed anywhere on the template. The rulers on the template correspond exactly to the rulers on the laser cutter, so if your sheet of plastic is smaller than the cutting area of the laser cutter, be sure that the drawing lies entirely within the necessary dimensions. The sheet is normally placed in the top left corner, using the rulers as a square corner, so place your drawings here.<br /> <br /> ==Using the Laser Cutter==<br /> ===Fumes Release Valve===<br /> ===Setting the Laser Height===<br /> ===Printing to the Laser Cutter===</div>

NathanHenry https://hades.mech.northwestern.edu//index.php?title=Laser_cutter&diff=13040 2009-04-02T18:51:00Z

<p>NathanHenry: </p> <hr /> <div>[[Image:laser_cutter_pic|thumb|right|250px|Laser Cutter]]<br /> ==Overview==<br /> <br /> The laser cutter, available in the prototyping lab, is an extremely useful tool for quickly cutting 2-D plastic parts. The machine uses a high intensity IR laser to cut any two dimensional design out of a plastic sheet. Acrylic is by far the best material for use with the laser cutter; when acrylic is used, the tool is capable of cutting through up to a 1/2&quot; thick piece.<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> '''If you are using a plastic other than acrylic, consult with the shop staff before cutting.'''<br /> &lt;br&gt;<br /> '''If you have never used the laser cutter before, ask for help if you encounter any problems. '''<br /> &lt;br clear=all&gt;<br /> <br /> ==Creating and Importing a File==<br /> To print to the laser cutter, a drawing must be prepared in CorelDRAW and placed on the laser cutter template, found on the desktop of the laser cutter computer. Drawing simple shapes, such as squares and circles is easy in CorelDRAW, however, for most applications with more advanced geometry it is better to use a more sophisticated CAD program. To transport the geometry from a solid modeler, such as Unigraphics, the part must be saved in a two-dimensional format, such as .dxf or .dwg. The drawing can then be imported into CorelDRAW and printed.<br /> ===Creating a .DXF or .DWG===<br /> ===Importing Files===<br /> <br /> ==Using the Laser Cutter==<br /> ===Fumes Release Valve===<br /> ===Setting the Laser Height===<br /> ===Printing to the Laser Cutter===</div>

NathanHenry https://hades.mech.northwestern.edu//index.php?title=Laser_cutter&diff=13039 2009-04-02T18:44:32Z

<p>NathanHenry: </p> <hr /> <div>[[Image:laser_cutter_pic|thumb|right|250px|Laser Cutter]]<br /> ==Overview==<br /> <br /> The laser cutter, available in the prototyping lab, is an extremely useful tool for quickly cutting 2-D plastic parts. The machine uses a high intensity IR laser to cut any two dimensional design out of a plastic sheet. Acrylic is by far the best material for use with the laser cutter; when acrylic is used, the tool is capable of cutting through up to a 1/2&quot; thick piece.<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> '''If you are using a plastic other than acrylic, consult with the shop staff before cutting.'''<br /> &lt;br&gt;<br /> '''If you have never used the laser cutter before, ask for help if you encounter any problems. '''<br /> &lt;br clear=all&gt;<br /> <br /> ==Creating and Importing a File==<br /> ===Creating a .DXF or .DWG===<br /> ===Importing Files===<br /> <br /> ==Using the Laser Cutter==<br /> ===Fumes Release Valve===<br /> ===Setting the Laser Height===<br /> ===Printing to the Laser Cutter===</div>

NathanHenry https://hades.mech.northwestern.edu//index.php?title=Laser_cutter&diff=13038 2009-04-02T18:42:59Z

<p>NathanHenry: </p> <hr /> <div>[[Image:laser_cutter_pic|thumb|right|300px|Laser Cutter]]<br /> ==Overview==<br /> <br /> The laser cutter, available in the prototyping lab, is an extremely useful tool for quickly cutting 2-D plastic parts. The machine uses a high intensity IR laser to cut any two dimensional design out of a plastic sheet. Acrylic is by far the best material for use with the laser cutter; when acrylic is used, the tool is capable of cutting through up to a 1/2&quot; thick piece.<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> '''If you are using a plastic other than acrylic, consult with the shop staff before cutting.'''<br /> &lt;br&gt;<br /> '''If you have never used the laser cutter before, ask for help if you encounter any problems. '''<br /> &lt;br clear=all&gt;<br /> <br /> ==Creating and Importing a File==<br /> ===Creating a .DXF or .DWG===<br /> ===Importing Files===<br /> <br /> ==Using the Laser Cutter==<br /> ===Fumes Release Valve===<br /> ===Setting the Laser Height===<br /> ===Printing to the Laser Cutter===</div>

NathanHenry https://hades.mech.northwestern.edu//index.php?title=Laser_cutter&diff=13037 2009-04-02T18:41:18Z

<p>NathanHenry: /* Creating and Importing a File */</p> <hr /> <div>[[Image:laser_cutter_pic|thumb|right|300px|Laser Cutter]]<br /> ==Overview==<br /> <br /> The laser cutter, available in the prototyping lab, is an extremely useful tool for quickly cutting 2-D plastic parts. The machine uses a high intensity IR laser to cut any two dimensional design out of a plastic sheet. Acrylic is by far the best material for use with the laser cutter; when acrylic is used, the tool is capable of cutting through up to a 1/2&quot; thick piece.<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> '''If you are using a plastic other than acrylic, consult with the shop staff before cutting.'''<br /> &lt;br&gt;<br /> '''If you have never used the laser cutter before, ask for help if you encounter any problems. '''<br /> &lt;br clear=all&gt;<br /> <br /> ==Creating and Importing a File==<br /> =Creating a .DXF or .DWG=<br /> =Importing Files=<br /> <br /> ==Using the Laser Cutter==</div>

NathanHenry https://hades.mech.northwestern.edu//index.php?title=Laser_cutter&diff=13036 2009-04-02T18:40:47Z

<p>NathanHenry: </p> <hr /> <div>[[Image:laser_cutter_pic|thumb|right|300px|Laser Cutter]]<br /> ==Overview==<br /> <br /> The laser cutter, available in the prototyping lab, is an extremely useful tool for quickly cutting 2-D plastic parts. The machine uses a high intensity IR laser to cut any two dimensional design out of a plastic sheet. Acrylic is by far the best material for use with the laser cutter; when acrylic is used, the tool is capable of cutting through up to a 1/2&quot; thick piece.<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> '''If you are using a plastic other than acrylic, consult with the shop staff before cutting.'''<br /> &lt;br&gt;<br /> '''If you have never used the laser cutter before, ask for help if you encounter any problems. '''<br /> &lt;br clear=all&gt;<br /> <br /> ==Creating and Importing a File==<br /> ==Using the Laser Cutter==</div>

NathanHenry https://hades.mech.northwestern.edu//index.php?title=Laser_cutter&diff=13035 2009-04-02T18:40:37Z

<p>NathanHenry: /* Overview */</p> <hr /> <div>==Overview==<br /> <br /> The laser cutter, available in the prototyping lab, is an extremely useful tool for quickly cutting 2-D plastic parts. The machine uses a high intensity IR laser to cut any two dimensional design out of a plastic sheet. Acrylic is by far the best material for use with the laser cutter; when acrylic is used, the tool is capable of cutting through up to a 1/2&quot; thick piece.<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> '''If you are using a plastic other than acrylic, consult with the shop staff before cutting.'''<br /> &lt;br&gt;<br /> '''If you have never used the laser cutter before, ask for help if you encounter any problems. '''<br /> &lt;br clear=all&gt;<br /> <br /> ==Creating and Importing a File==<br /> ==Using the Laser Cutter==</div>

NathanHenry https://hades.mech.northwestern.edu//index.php?title=Laser_cutter&diff=13034 2009-04-02T18:37:54Z

<p>NathanHenry: /* Overview */</p> <hr /> <div>==Overview==<br /> [[Image:laser_cutter_pic|thumb|right|300px|Laser Cutter]]<br /> The laser cutter, available in the prototyping lab, is an extremely useful tool for quickly cutting 2-D plastic parts. The machine uses a high intensity IR laser to cut any two dimensional design out of a plastic sheet. Acrylic is by far the best material for use with the laser cutter; when acrylic is used, the tool is capable of cutting through up to a 1/2&quot; thick piece.<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> '''If you are using a plastic other than acrylic, consult with the shop staff before cutting.'''<br /> &lt;br&gt;<br /> '''If you have never used the laser cutter before, ask for help if you encounter any problems. '''<br /> &lt;br clear=all&gt;<br /> <br /> ==Creating and Importing a File==<br /> ==Using the Laser Cutter==</div>

NathanHenry https://hades.mech.northwestern.edu//index.php?title=File:Laser_cutter_pic&diff=13033 2009-04-02T18:37:02Z

<p>NathanHenry: </p> <hr /> <div></div>

NathanHenry https://hades.mech.northwestern.edu//index.php?title=Laser_cutter&diff=13032 2009-04-02T18:36:49Z

<p>NathanHenry: /* Overview */</p> <hr /> <div>==Overview==<br /> [[Image:laser_cutter_pic|thumb|right|200px|Laser Cutter]]<br /> The laser cutter, available in the prototyping lab, is an extremely useful tool for quickly cutting 2-D plastic parts. The machine uses a high intensity IR laser to cut any two dimensional design out of a plastic sheet. Acrylic is by far the best material for use with the laser cutter; when acrylic is used, the tool is capable of cutting through up to a 1/2&quot; thick piece.<br /> &lt;br&gt;<br /> '''If you are using a plastic other than acrylic, consult with the shop staff before cutting.'''<br /> &lt;br&gt;<br /> '''If you have never used the laser cutter before, ask for help if you encounter any problems. '''<br /> <br /> ==Creating and Importing a File==<br /> ==Using the Laser Cutter==</div>

NathanHenry https://hades.mech.northwestern.edu//index.php?title=Laser_cutter&diff=13031 2009-04-02T18:34:00Z

<p>NathanHenry: /* Overview */</p> <hr /> <div>==Overview==<br /> The laser cutter, available in the prototyping lab, is an extremely useful tool for quickly cutting 2-D plastic parts. The machine uses a high intensity IR laser to cut any two dimensional design out of a plastic sheet. Acrylic is by far the best material for use with the laser cutter; when acrylic is used, the tool is capable of cutting through up to a 1/2&quot; thick piece.<br /> &lt;br&gt;<br /> '''If you are using a plastic other than acrylic, consult with the shop staff before cutting.'''<br /> &lt;br&gt;<br /> '''If you have never used the laser cutter before, ask for help if you encounter any problems. '''<br /> <br /> ==Creating and Importing a File==<br /> ==Using the Laser Cutter==</div>

NathanHenry https://hades.mech.northwestern.edu//index.php?title=Laser_cutter&diff=13030 2009-04-02T18:33:29Z

<p>NathanHenry: /* Overview */</p> <hr /> <div>==Overview==<br /> The laser cutter, available in the prototyping lab, is an extremely useful tool for quickly cutting 2-D plastic parts. The machine uses a high intensity IR laser to cut any two dimensional design out of a plastic sheet. Acrylic is by far the best material for use with the laser cutter; when acrylic is used, the tool is capable of cutting through up to a 1/2&quot; thick piece.<br /> '''If you are using a plastic other than acrylic, consult with the shop staff before cutting.<br /> If you have never used the laser cutter before, ask for help if you encounter any problems. '''<br /> <br /> ==Creating and Importing a File==<br /> ==Using the Laser Cutter==</div>

NathanHenry https://hades.mech.northwestern.edu//index.php?title=Laser_cutter&diff=13029 2009-04-02T18:21:18Z

<p>NathanHenry: </p> <hr /> <div>==Overview==<br /> ==Creating and Importing a File==<br /> ==Using the Laser Cutter==</div>

NathanHenry https://hades.mech.northwestern.edu//index.php?title=Monkeybot&diff=13028 2009-04-02T18:20:12Z

<p>NathanHenry: /* Design Considerations */</p> <hr /> <div>[[Image:monkeybot_pic|thumb|right|350px|Moneybot]]<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> <br /> ==Team Members==<br /> [[Image:Nathan_and_Nelson|thumb|right|200px|Nelson Rosa, Nathan Henry]]<br /> Nathan Henry - Senior, Mechanical Engineering&lt;br&gt;<br /> Nelson Rosa - Ph.D Student, Mechanical Engineering<br /> &lt;br clear=all&gt;<br /> <br /> ==Overview==<br /> The goal of this project was to create a brachiating robot capable of swinging itself side to side or climbing. This two link robot has [http://catalog.apwcompany.com/item/electromagnets/1-0-diameter-round-br-em100/em100-6-122?&amp;seo=110 electro-magnets] on each end and a [[Actuators Available in the Mechatronics Lab | DC motor]] at the pivot. With one magnet on, the robot swings under gravity and is aided by a input torque from the motor. This torque allows the swinging robot to overcome friction and pump energy into the system. Once the swinging arm has enough energy, the second magnet reaches a point at the same height or above the first magnet. At this point, the second magnet is turned on the motor is turned off. Now the process is repeated, swinging on the second magnet.<br /> <br /> We attempted to control the motor using both a closed loop control, with [http://www.usa.canon.com/html/industrial_encoders/lre_tr36.html rotary encoders], and an open loop control, using a time based algorithm.<br /> <br /> [http://www.youtube.com/watch?v=TA2VcH_GDJ0 Video of the monkeybot climbing]<br /> <br /> ==Geometry==<br /> [[Image:Monkeybot Geometry|thumb|left|200px|Monkeybot Geometry]]<br /> The monkeybot behaves like a double-pendulum system. The geometry, and our definitions of angles is shown to the right. The two angles important to us are the angle between the top link and a horizontal reference, and the angle between the two links. The rotary encoders over the magnet provide a measurement of the first angel, while the motor encoder measures the second.<br /> <br /> With these two angles we are able to implement a variety of control laws as described below. <br /> &lt;br clear=all&gt;<br /> <br /> ==Simulation==<br /> We developed a simulation that shows how the brachiating robot would ideally climb given a closed-loop control law that continuously pumps energy into the system. The simulation assumes point mass objects (red dots), viscous friction at the revolute joints, and an input forcing function at the motor joint (middle red dot). The simulation was done in Mathematica 7.0 and the code is hosted as a [http://code.google.com/p/hoppingrobot/ Google code project].<br /> <br /> ==Control Method==<br /> <br /> ===Closed Loop Control===<br /> [[Image:Rotary_Encoder_TR_36|thumb|right|200px|Laser Rotary Encoder]]<br /> We first attempted to control the DC motor using feedback from a [http://www.usa.canon.com/html/industrial_encoders/lre_tr36.html rotary encoder] placed directly over each magnet. From this encoder, using both the A and B channels, we are able to determine the sign of the top link's velocity. We then implemented a simple control law in which the motor is full on in the same direction that the top link is rotating (switching only when the sign of the velocity changed). This causes the lower link to pump in phase with the top link, mimicking the motion of a person on a swing set.<br /> <br /> With this control law we were able to pump energy into the system, however, we were never able to add enough energy to get the bottom magnet to a height equal to or above the top magnet. Starting from a resting position, with the lower link dangling straight down, the bottom link pumps in phase with the top link. The bottom magnet gradually gets higher and higher, but seems to stop increasing when it reaches a height slightly below the fixed magnet. Friction seems to be the main reason why the robot can not climb.<br /> <br /> We also implemented a control law where the lower link pumped out of phase with the top link. This caused a large increase in the movement of the top link, however, the bottom magnet stays in nearly the same position throughout.<br /> <br /> &lt;br clear=all&gt;<br /> <br /> ===Open Loop Control===<br /> Our second approach was an open loop, time based algorithm. It involves no feedback and is just a simple set of commands implemented by the PIC. In order for the monkeybot to climb, the first link must be started with some potential energy. The magnets are both on and at the same height when the algorithm begins. The algorithm is as follows, it can be tuned by changing the values A,B,C,D which are on the order of 500-600 milliseconds.<br /> <br /> Release magnet one<br /> Motor on counterclockwise for A milliseconds<br /> Motor off<br /> Magnet one on<br /> Release magnet two<br /> Motor on counterclockwise for B milliseconds<br /> Motor off<br /> Magnet two on<br /> Release magnet two<br /> Motor on clockwise for C milliseconds<br /> Motor off<br /> Magnet two on<br /> Release magnet one<br /> Motor on clockwise for D milliseconds<br /> Motor off<br /> Magnet one on<br /> <br /> This process is repeated, and overtime, the monkeybot climbs. A video of this can be found [http://www.youtube.com/watch?v=TA2VcH_GDJ0 here.]<br /> <br /> ==Mechanical Design==<br /> ===Parts List===<br /> The robot contains:<br /> <br /> Two acrylic links<br /> Two rotational ball-bearings<br /> Two [http://catalog.apwcompany.com/item/electromagnets/1-0-diameter-round-br-em100/em100-6-122?&amp;seo=110 electro-magnets]<br /> Two [http://www.usa.canon.com/html/industrial_encoders/lre_tr36.html rotary encoders]<br /> One [[Media:pittmangearmotor.pdf|Pittmann GM8224]] [[Actuators Available in the Mechatronics Lab |DC Motor]] with 19.5:1 Gear Head<br /> One large steel surface<br /> <br /> ===Design Considerations===<br /> The two links, made of 1/8” thick acrylic, create the body of the robot and create a mount for both bearings and the motor. The thickness and the material was chosen to minimize weight, and thus the torque required to swing the robot. The links were produced using a [[laser cutter | Laser Cutter]]. The rotational ball bearings mount on the links and hold the magnets, allowing the robot to swing around a fixed point. The encoders are mounted above the magnets on a bridge, so that they are capable of measuring the rotation of the link around the magnet.<br /> <br /> The Pittman motor was chosen to provide enough torque to the links to overcome friction. The gear head is also needed to get the necessary torque. With the gear head, the Pittmann is capable of providing 2.1 Nm of torque, which is more than enough for this application. However, the motor is rather large and thus increases the overall weight of the system.<br /> <br /> The data sheet for the Pittamnn motor can be found [[Media:pittmangearmotor.pdf|here]].<br /> <br /> ==Electrical Design==<br /> ===Parts List===<br /> The robot contains:<br /> <br /> One PIC 18F4250 @ 40 MHz<br /> Two 74HC00 Quad 2-input NAND<br /> One L293B four half H-bridges<br /> Terminal strips (enough for ten connections)<br /> Two 10-pin headers (for rotary encoders)<br /> Two TIP31C NPN Power Transistor TO-220<br /> One [http://www.lsicsi.com/pdfs/Data_Sheets/LS7083_LS7084.pdf LS7083] Quadrature Clock Converter<br /> <br /> ===Design Considerations===<br /> As the central processing unit, the PIC controlled the magnets, motor, and rotary encoders. Below is a block diagram of the circuit. The multiplexer circuit was built with NAND gates and cut down on the redundant circuitry that would have been needed to interface with both rotary encoders individually. The decision to use the terminal strips allowed us to modularize the interface between the PIC and the rest of the circuit. For example, our closed-loop control law could have made use of the angular position of either the fixed pivot or the motor pivot in an attempt to pump energy into the system. The terminal strips allowed us to easily and quickly make the changes without the need to reprogram the PIC in order to test which approach was better.<br /> <br /> The circuit design was originally meant for the PIC 18F4331 with its built-in hardware quadrature decoder interface for reading the fixed pivot angular position or velocity. The LS7803 was meant to complement the built-in quadrature decoder by reading in values from the motor encoder allowing us to know the relative position of the robot on the magnetic surface. Instead, the PIC18F4520 was used throughout our project and the LS7803 became a convenient way to detect change of velocity direction useful for our [[Monkeybot#Closed_Loop_Control | closed-loop controller]].<br /> <br /> <br /> [[Image:monkeybot-block.png|thumb|center|600px|Circuit Block Diagram]]<br /> <br /> ==Code==<br /> <br /> The implemented code is straightforward. The main program sits in a loop waiting for commands from an RS-232 connection. For example, whenever the user hits 'o' a preprogrammed timing sequence (i.e. the [[Monkeybot#Open_Loop_Control | open-loop controller]]) is executed that enables the robot to climb. As seen in the [http://www.youtube.com/watch?v=TA2VcH_GDJ0 video], we swing counter-clockwise twice and then clockwise twice to avoid the wires from tangling up with each other.<br /> <br /> Although commented out, the closed-loop controller can be activated by inserting an empty infinite loop and enabling the commented interrupts. We made use of the Capture/Compare/PWM modules, CCP1 and CCP2, on the PIC. As configured, every 16th rising edge of the LS7803 quadrature up or down pulse for the CCP1 and CCP2 module, respectively, generated an interrupt. It is important to note that, if sampled correctly, an up or down pulse is a mutually exclusive event on the LS7803. Because each pulse represented a +/-1 increment to our position counter, every time an interrupt occurred, we would know the sign of a links velocity by the interrupt that was triggered. We used this information to switch motor direction in our [[Monkeybot#Open_Loop_Control | closed-loop controller]].<br /> <br /> We have attached the code as-is for educational purposes only. Here is the zip file containing the entire PIC-C project files for the [[Media:monkeybot.zip|code]].<br /> <br /> ==Results and Reflections==<br /> We successfully created a climbing robot, however, the monkeybot was not as intelligent as we had originally hoped. It was unable to swing itself up from rest using a variety of closed loop control laws, most likely due to the large amounts of friction. To combat the high friction, we started the swinging link with some potential energy. From that point, it was relatively simple to design and tune an open loop time based algorithm which causes the robot to climb.<br /> <br /> A closed loop control system using encoders on both the magnets and the motor would improve this project. With this feedback, all of the necessary angles are known and thus the state of the robot is known at all times. If the robot knows its own position, it is better able to adjust to errors, such as a magnet slipping or variations in friction. An open loop time based algorithm can not adjust itself, as the timing of the sequence is hard coded.</div>

NathanHenry https://hades.mech.northwestern.edu//index.php?title=Monkeybot&diff=12693 2009-03-20T04:08:53Z

<p>NathanHenry: </p> <hr /> <div>[[Image:monkeybot_pic|thumb|right|350px|Moneybot]]<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> <br /> ==Team Members==<br /> [[Image:Nathan_and_Nelson|thumb|right|200px|Nelson Rosa, Nathan Henry]]<br /> Nathan Henry - Senior, Mechanical Engineering&lt;br&gt;<br /> Nelson Rosa - Ph.D Student, Mechanical Engineering<br /> &lt;br clear=all&gt;<br /> <br /> ==Overview==<br /> The goal of this project was to create a brachiating robot capable of swinging itself side to side or climbing. This two link robot has [http://catalog.apwcompany.com/item/electromagnets/1-0-diameter-round-br-em100/em100-6-122?&amp;seo=110 electro-magnets] on each end and a [[Actuators Available in the Mechatronics Lab | DC motor]] at the pivot. With one magnet on, the robot swings under gravity and is aided by a input torque from the motor. This torque allows the swinging robot to overcome friction and pump energy into the system. Once the swinging arm has enough energy, the second magnet reaches a point at the same height or above the first magnet. At this point, the second magnet is turned on the motor is turned off. Now the process is repeated, swinging on the second magnet.<br /> <br /> We attempted to control the motor using both a closed loop control, with [http://www.usa.canon.com/html/industrial_encoders/lre_tr36.html rotary encoders], and an open loop control, using a time based algorithm.<br /> <br /> [http://www.youtube.com/watch?v=TA2VcH_GDJ0 Video of the monkeybot climbing]<br /> <br /> ==Geometry==<br /> [[Image:Monkeybot Geometry|thumb|left|200px|Monkeybot Geometry]]<br /> The monkeybot behaves like a double-pendulum system. The geometry, and our definitions of angles is shown to the right. The two angles important to us are the angle between the top link and a horizontal reference, and the angle between the two links. The rotary encoders over the magnet provide a measurement of the first angel, while the motor encoder measures the second.<br /> <br /> With these two angles we are able to implement a variety of control laws as described below. <br /> &lt;br clear=all&gt;<br /> <br /> ==Control Method==<br /> <br /> ===Closed Loop Control===<br /> [[Image:Rotary_Encoder_TR_36|thumb|right|200px|Laser Rotary Encoder]]<br /> We first attempted to control the DC motor using feedback from a [http://www.usa.canon.com/html/industrial_encoders/lre_tr36.html rotary encoder] placed directly over each magnet. From this encoder, using both the A and B channels, we are able to determine the sign of the top link's velocity. We then implemented a simple control law in which the motor is full on in the same direction that the top link is rotating. This causes the lower link to pump in phase with the top link, mimicking the motion of a person on a swing set.<br /> <br /> With this control law we were able to pump energy into the system, however, we were never able to add enough energy to get the bottom magnet to a height equal to or above the top magnet. Starting from a resting position, with the lower link dangling straight down, the bottom link pumps in phase with the top link. The bottom magnet gradually gets higher and higher, but seems to stop increasing when it reaches a height slightly below the fixed magnet. Friction seems to be the main reason why the robot can not climb.<br /> <br /> We also implemented a control law where the lower link pumped out of phase with the top link. This caused a large increase in the movement of the top link, however, the bottom magnet stays in nearly the same position throughout.<br /> <br /> &lt;br clear=all&gt;<br /> <br /> ===Open Loop Control===<br /> Our second approach was an open loop, time based algorithm. It involves no feedback and is just a simple set of commands implemented by the PIC. In order for the monkeybot to climb, the first link must be started with some potential energy. The magnets are both on and at the same height when the algorithm begins. The algorithm is as follows, it can be tuned by changing the values A,B,C,D which are on the order of 500-600 milliseconds.<br /> <br /> Release magnet one<br /> Motor on counterclockwise for A milliseconds<br /> Motor off<br /> Magnet one on<br /> Release magnet two<br /> Motor on counterclockwise for B milliseconds<br /> Motor off<br /> Magnet two on<br /> Release magnet two<br /> Motor on clockwise for C milliseconds<br /> Motor off<br /> Magnet two on<br /> Release magnet one<br /> Motor on clockwise for D milliseconds<br /> Motor off<br /> Magnet one on<br /> <br /> This process is repeated, and overtime, the monkeybot climbs. A video of this can be found [http://www.youtube.com/watch?v=TA2VcH_GDJ0 here.]<br /> <br /> ==Mechanical Design==<br /> ===Parts List===<br /> The robot contains:<br /> <br /> Two acrylic links<br /> Two rotational ball-bearings<br /> Two [http://catalog.apwcompany.com/item/electromagnets/1-0-diameter-round-br-em100/em100-6-122?&amp;seo=110 electro-magnets]<br /> Two [http://www.usa.canon.com/html/industrial_encoders/lre_tr36.html rotary encoders]<br /> One [[Media:pittmangearmotor.pdf|Pittmann GM8224]] [[Actuators Available in the Mechatronics Lab |DC Motor]] with 19.5:1 Gear Head<br /> <br /> ===Design Considerations===<br /> The two links, made of 1/8” thick acrylic, create the body of the robot and create a mount for both bearings and the motor. The thickness and the material was chosen to minimize weight, and thus the torque required to swing the robot. The links were produced using a laser cutter. The rotational ball bearings mount on the links and hold the magnets, allowing the robot to swing around a fixed point. The encoders are mounted above the magnets on a bridge, so that they are capable of measuring the rotation of the link around the magnet.<br /> <br /> The Pittman motor was chosen to provide enough torque to the links to overcome friction. The gear head is also needed to get the necessary torque. With the gear head, the Pittmann is capable of providing 2.1 Nm of torque, which is more than enough for this application. However, the motor is rather large and thus increases the overall weight of the system.<br /> <br /> The data sheet for the Pittamnn motor can be found [[Media:pittmangearmotor.pdf|here]].<br /> <br /> ==Electrical Design==<br /> <br /> ==Code==<br /> <br /> ==Results and Reflections==<br /> We successfully created a climbing robot, however, the monkeybot was not as intelligent as we had originally hoped. It was unable to swing itself up from rest using a variety of closed loop control laws, most likely due to the large amounts of friction. To combat the high friction, we started the swinging link with some potential energy. From that point, it was relatively simple to design and tune an open loop time based algorithm which causes the robot to climb.<br /> <br /> A closed loop control system using encoders on both the magnets and the motor would improve this project. With this feedback, all of the necessary angles are known and thus the state of the robot is known at all times. If the robot knows its own position, it is better able to adjust to errors, such as a magnet slipping or variations in friction. An open loop time based algorithm can not adjust itself, as the timing of the sequence is hard coded.</div>

NathanHenry https://hades.mech.northwestern.edu//index.php?title=Monkeybot&diff=12681 2009-03-20T03:47:58Z

<p>NathanHenry: /* Closed Loop Control */</p> <hr /> <div>[[Image:monkeybot_pic|thumb|right|350px|Moneybot Picture]]<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> <br /> ==Team Members==<br /> [[Image:Nathan_and_Nelson|thumb|right|200px|Nelson Rosa, Nathan Henry]]<br /> Nathan Henry - Senior, Mechanical Engineering&lt;br&gt;<br /> Nelson Rosa - Ph.D Student, Mechanical Engineering<br /> &lt;br clear=all&gt;<br /> <br /> ==Overview==<br /> The goal of this project was to create a brachiating robot capable of swinging itself side to side or climbing. This two link robot has [http://catalog.apwcompany.com/item/electromagnets/1-0-diameter-round-br-em100/em100-6-122?&amp;seo=110 electro-magnets] on each end and a [[Actuators Available in the Mechatronics Lab | DC motor]] at the pivot. With one magnet on, the robot swings under gravity and is aided by a input torque from the motor. This torque allows the swinging robot to overcome friction and pump energy into the system. Once the swinging arm has enough energy, the second magnet reaches a point at the same height or above the first magnet. At this point, the second magnet is turned on the motor is turned off. Now the process is repeated, swinging on the second magnet.<br /> <br /> We attempted to control the motor using both a closed loop control, with [http://www.usa.canon.com/html/industrial_encoders/lre_tr36.html rotary encoders], and an open loop control, using a time based algorithm.<br /> <br /> [http://www.youtube.com/watch?v=TA2VcH_GDJ0 Video of the monkeybot climbing]<br /> <br /> ==Geometry==<br /> [[Image:Monkeybot Geometry|thumb|left|200px|Monkeybot Geometry]]<br /> The monkeybot behaves like a double-pendulum system. The geometry, and our definitions of angles is shown to the right. The two angles important to us are the angle between the top link and a horizontal reference, and the angle between the two links. The rotary encoders over the magnet provide a measurement of the first angel, while the motor encoder measures the second.<br /> <br /> With these two angles we are able to implement a variety of control laws as described below. <br /> &lt;br clear=all&gt;<br /> <br /> ==Control Method==<br /> <br /> ===Closed Loop Control===<br /> [[Image:Rotary_Encoder_TR_36|thumb|right|200px|Laser Rotary Encoder]]<br /> We first attempted to control the DC motor using feedback from a [http://www.usa.canon.com/html/industrial_encoders/lre_tr36.html rotary encoder] placed directly over each magnet. From this encoder, using both the A and B channels, we are able to determine the sign of the top link's velocity. We then implemented a simple control law in which the motor is full on in the same direction that the top link is rotating. This causes the lower link to pump in phase with the top link, mimicking the motion of a person on a swing set.<br /> <br /> With this control law we were able to pump energy into the system, however, we were never able to add enough energy to get the bottom magnet to a height equal to or above the top magnet. Starting from a resting position, with the lower link dangling straight down, the bottom link pumps in phase with the top link. The bottom magnet gradually gets higher and higher, but seems to stop increasing when it reaches a height slightly below the fixed magnet. Friction seems to be the main reason why the robot can not climb.<br /> <br /> We also implemented a control law where the lower link pumped out of phase with the top link. This caused a large increase in the movement of the top link, however, the bottom magnet stays in nearly the same position throughout.<br /> <br /> &lt;br clear=all&gt;<br /> <br /> ===Open Loop Control===<br /> Our second approach was an open loop, time based algorithm. It involves no feedback and is just a simple set of commands implemented by the PIC. In order for the monkeybot to climb, the first link must be started with some potential energy. The magnets are both on and at the same height when the algorithm begins. The algorithm is as follows, it can be tuned by changing the values A,B,C,D which are on the order of 500-600 milliseconds.<br /> <br /> Release magnet one<br /> Motor on counterclockwise for A milliseconds<br /> Motor off<br /> Magnet one on<br /> Release magnet two<br /> Motor on counterclockwise for B milliseconds<br /> Motor off<br /> Magnet two on<br /> Release magnet two<br /> Motor on clockwise for C milliseconds<br /> Motor off<br /> Magnet two on<br /> Release magnet one<br /> Motor on clockwise for D milliseconds<br /> Motor off<br /> Magnet one on<br /> <br /> This process is repeated, and overtime, the monkeybot climbs. A video of this can be found [http://www.youtube.com/watch?v=TA2VcH_GDJ0 here.]<br /> <br /> ==Mechanical Design==<br /> ===Parts List===<br /> The robot contains:<br /> <br /> Two acrylic links<br /> Two rotational ball-bearings<br /> Two [http://catalog.apwcompany.com/item/electromagnets/1-0-diameter-round-br-em100/em100-6-122?&amp;seo=110 electro-magnets]<br /> Two [http://www.usa.canon.com/html/industrial_encoders/lre_tr36.html rotary encoders]<br /> One [[Media:pittmangearmotor.pdf|Pittmann GM8224]] [[Actuators Available in the Mechatronics Lab |DC Motor]] with 19.5:1 Gear Head<br /> <br /> ===Design Considerations===<br /> The two links, made of 1/8” thick acrylic, create the body of the robot and create a mount for both bearings and the motor. The thickness and the material was chosen to minimize weight, and thus the torque required to swing the robot. The links were produced using a laser cutter. The rotational ball bearings mount on the links and hold the magnets, allowing the robot to swing around a fixed point. The encoders are mounted above the magnets on a bridge, so that they are capable of measuring the rotation of the link around the magnet.<br /> <br /> The Pittman motor was chosen to provide enough torque to the links to overcome friction. The gear head is also needed to get the necessary torque. With the gear head, the Pittmann is capable of providing 2.1 Nm of torque, which is more than enough for this application. However, the motor is rather large and thus increases the overall weight of the system.<br /> <br /> The data sheet for the Pittamnn motor can be found [[Media:pittmangearmotor.pdf|here]].<br /> <br /> ==Electrical Design==<br /> <br /> ==Code==<br /> <br /> ==Results and Reflections==<br /> We successfully created a climbing robot, however, the monkeybot was not as intelligent as we had originally hoped. It was unable to swing itself up from rest using a variety of closed loop control laws, most likely due to the large amounts of friction. To combat the high friction, we started the swinging link with some potential energy. From that point, it was relatively simple to design and tune an open loop time based algorithm which causes the robot to climb.<br /> <br /> A closed loop control system using encoders on both the magnets and the motor would improve this project. With this feedback, all of the necessary angles are known and thus the state of the robot is known at all times. If the robot knows its own position, it is better able to adjust to errors, such as a magnet slipping or variations in friction. An open loop time based algorithm can not adjust itself, as the timing of the sequence is hard coded.</div>

NathanHenry https://hades.mech.northwestern.edu//index.php?title=Monkeybot&diff=12679 2009-03-20T03:47:36Z

<p>NathanHenry: /* Geometry */</p> <hr /> <div>[[Image:monkeybot_pic|thumb|right|350px|Moneybot Picture]]<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> <br /> ==Team Members==<br /> [[Image:Nathan_and_Nelson|thumb|right|200px|Nelson Rosa, Nathan Henry]]<br /> Nathan Henry - Senior, Mechanical Engineering&lt;br&gt;<br /> Nelson Rosa - Ph.D Student, Mechanical Engineering<br /> &lt;br clear=all&gt;<br /> <br /> ==Overview==<br /> The goal of this project was to create a brachiating robot capable of swinging itself side to side or climbing. This two link robot has [http://catalog.apwcompany.com/item/electromagnets/1-0-diameter-round-br-em100/em100-6-122?&amp;seo=110 electro-magnets] on each end and a [[Actuators Available in the Mechatronics Lab | DC motor]] at the pivot. With one magnet on, the robot swings under gravity and is aided by a input torque from the motor. This torque allows the swinging robot to overcome friction and pump energy into the system. Once the swinging arm has enough energy, the second magnet reaches a point at the same height or above the first magnet. At this point, the second magnet is turned on the motor is turned off. Now the process is repeated, swinging on the second magnet.<br /> <br /> We attempted to control the motor using both a closed loop control, with [http://www.usa.canon.com/html/industrial_encoders/lre_tr36.html rotary encoders], and an open loop control, using a time based algorithm.<br /> <br /> [http://www.youtube.com/watch?v=TA2VcH_GDJ0 Video of the monkeybot climbing]<br /> <br /> ==Geometry==<br /> [[Image:Monkeybot Geometry|thumb|left|200px|Monkeybot Geometry]]<br /> The monkeybot behaves like a double-pendulum system. The geometry, and our definitions of angles is shown to the right. The two angles important to us are the angle between the top link and a horizontal reference, and the angle between the two links. The rotary encoders over the magnet provide a measurement of the first angel, while the motor encoder measures the second.<br /> <br /> With these two angles we are able to implement a variety of control laws as described below. <br /> &lt;br clear=all&gt;<br /> <br /> ==Control Method==<br /> <br /> ===Closed Loop Control===<br /> [[Image:Rotary_Encoder_TR_36|thumb|right|200px|Laser Rotary Encoder]]<br /> We first attempted to control the DC motor using feedback from a [http://www.usa.canon.com/html/industrial_encoders/lre_tr36.html rotary encoder] placed directly over each magnet. From this encoder, using both the A and B channels, we are able to determine the sign of the top link's velocity. We then implemented a simple control law in which the motor is full on in the same direction that the top link is rotating. This causes the lower link to pump in phase with the top link, mimicking the motion of a person on a swing set.<br /> <br /> With this control law we were able to pump energy into the system, however, we were never able to add enough energy to get the bottom magnet to a height equal to or above the top magnet. Starting from a resting position, with the lower link dangling straight down, the bottom link pumps in phase with the top link. The bottom magnet gradually gets higher and higher, but seems to stop increasing when it reaches a height slightly below the fixed magnet. Friction seems to be the main reason why the robot can not climb.<br /> <br /> We also implemented a control law where the lower link pumped out of phase with the top link. This caused a large increase in the movement of the top link, however, the bottom magnet stays in nearly the same position throughout.<br /> <br /> &lt;br&gt;<br /> &lt;br&gt;<br /> <br /> ===Open Loop Control===<br /> Our second approach was an open loop, time based algorithm. It involves no feedback and is just a simple set of commands implemented by the PIC. In order for the monkeybot to climb, the first link must be started with some potential energy. The magnets are both on and at the same height when the algorithm begins. The algorithm is as follows, it can be tuned by changing the values A,B,C,D which are on the order of 500-600 milliseconds.<br /> <br /> Release magnet one<br /> Motor on counterclockwise for A milliseconds<br /> Motor off<br /> Magnet one on<br /> Release magnet two<br /> Motor on counterclockwise for B milliseconds<br /> Motor off<br /> Magnet two on<br /> Release magnet two<br /> Motor on clockwise for C milliseconds<br /> Motor off<br /> Magnet two on<br /> Release magnet one<br /> Motor on clockwise for D milliseconds<br /> Motor off<br /> Magnet one on<br /> <br /> This process is repeated, and overtime, the monkeybot climbs. A video of this can be found [http://www.youtube.com/watch?v=TA2VcH_GDJ0 here.]<br /> <br /> ==Mechanical Design==<br /> ===Parts List===<br /> The robot contains:<br /> <br /> Two acrylic links<br /> Two rotational ball-bearings<br /> Two [http://catalog.apwcompany.com/item/electromagnets/1-0-diameter-round-br-em100/em100-6-122?&amp;seo=110 electro-magnets]<br /> Two [http://www.usa.canon.com/html/industrial_encoders/lre_tr36.html rotary encoders]<br /> One [[Media:pittmangearmotor.pdf|Pittmann GM8224]] [[Actuators Available in the Mechatronics Lab |DC Motor]] with 19.5:1 Gear Head<br /> <br /> ===Design Considerations===<br /> The two links, made of 1/8” thick acrylic, create the body of the robot and create a mount for both bearings and the motor. The thickness and the material was chosen to minimize weight, and thus the torque required to swing the robot. The links were produced using a laser cutter. The rotational ball bearings mount on the links and hold the magnets, allowing the robot to swing around a fixed point. The encoders are mounted above the magnets on a bridge, so that they are capable of measuring the rotation of the link around the magnet.<br /> <br /> The Pittman motor was chosen to provide enough torque to the links to overcome friction. The gear head is also needed to get the necessary torque. With the gear head, the Pittmann is capable of providing 2.1 Nm of torque, which is more than enough for this application. However, the motor is rather large and thus increases the overall weight of the system.<br /> <br /> The data sheet for the Pittamnn motor can be found [[Media:pittmangearmotor.pdf|here]].<br /> <br /> ==Electrical Design==<br /> <br /> ==Code==<br /> <br /> ==Results and Reflections==<br /> We successfully created a climbing robot, however, the monkeybot was not as intelligent as we had originally hoped. It was unable to swing itself up from rest using a variety of closed loop control laws, most likely due to the large amounts of friction. To combat the high friction, we started the swinging link with some potential energy. From that point, it was relatively simple to design and tune an open loop time based algorithm which causes the robot to climb.<br /> <br /> A closed loop control system using encoders on both the magnets and the motor would improve this project. With this feedback, all of the necessary angles are known and thus the state of the robot is known at all times. If the robot knows its own position, it is better able to adjust to errors, such as a magnet slipping or variations in friction. An open loop time based algorithm can not adjust itself, as the timing of the sequence is hard coded.</div>

NathanHenry https://hades.mech.northwestern.edu//index.php?title=Monkeybot&diff=12678 2009-03-20T03:47:16Z

<p>NathanHenry: </p> <hr /> <div>[[Image:monkeybot_pic|thumb|right|350px|Moneybot Picture]]<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> <br /> ==Team Members==<br /> [[Image:Nathan_and_Nelson|thumb|right|200px|Nelson Rosa, Nathan Henry]]<br /> Nathan Henry - Senior, Mechanical Engineering&lt;br&gt;<br /> Nelson Rosa - Ph.D Student, Mechanical Engineering<br /> &lt;br clear=all&gt;<br /> <br /> ==Overview==<br /> The goal of this project was to create a brachiating robot capable of swinging itself side to side or climbing. This two link robot has [http://catalog.apwcompany.com/item/electromagnets/1-0-diameter-round-br-em100/em100-6-122?&amp;seo=110 electro-magnets] on each end and a [[Actuators Available in the Mechatronics Lab | DC motor]] at the pivot. With one magnet on, the robot swings under gravity and is aided by a input torque from the motor. This torque allows the swinging robot to overcome friction and pump energy into the system. Once the swinging arm has enough energy, the second magnet reaches a point at the same height or above the first magnet. At this point, the second magnet is turned on the motor is turned off. Now the process is repeated, swinging on the second magnet.<br /> <br /> We attempted to control the motor using both a closed loop control, with [http://www.usa.canon.com/html/industrial_encoders/lre_tr36.html rotary encoders], and an open loop control, using a time based algorithm.<br /> <br /> [http://www.youtube.com/watch?v=TA2VcH_GDJ0 Video of the monkeybot climbing]<br /> <br /> ==Geometry==<br /> [[Image:Monkeybot Geometry|thumb|left|200px|Monkeybot Geometry]]<br /> The monkeybot behaves like a double-pendulum system. The geometry, and our definitions of angles is shown to the right. The two angles important to us are the angle between the top link and a horizontal reference, and the angle between the two links. The rotary encoders over the magnet provide a measurement of the first angel, while the motor encoder measures the second.<br /> <br /> With these two angles we are able to implement a variety of control laws as described below. <br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> <br /> ==Control Method==<br /> <br /> ===Closed Loop Control===<br /> [[Image:Rotary_Encoder_TR_36|thumb|right|200px|Laser Rotary Encoder]]<br /> We first attempted to control the DC motor using feedback from a [http://www.usa.canon.com/html/industrial_encoders/lre_tr36.html rotary encoder] placed directly over each magnet. From this encoder, using both the A and B channels, we are able to determine the sign of the top link's velocity. We then implemented a simple control law in which the motor is full on in the same direction that the top link is rotating. This causes the lower link to pump in phase with the top link, mimicking the motion of a person on a swing set.<br /> <br /> With this control law we were able to pump energy into the system, however, we were never able to add enough energy to get the bottom magnet to a height equal to or above the top magnet. Starting from a resting position, with the lower link dangling straight down, the bottom link pumps in phase with the top link. The bottom magnet gradually gets higher and higher, but seems to stop increasing when it reaches a height slightly below the fixed magnet. Friction seems to be the main reason why the robot can not climb.<br /> <br /> We also implemented a control law where the lower link pumped out of phase with the top link. This caused a large increase in the movement of the top link, however, the bottom magnet stays in nearly the same position throughout.<br /> <br /> &lt;br&gt;<br /> &lt;br&gt;<br /> <br /> ===Open Loop Control===<br /> Our second approach was an open loop, time based algorithm. It involves no feedback and is just a simple set of commands implemented by the PIC. In order for the monkeybot to climb, the first link must be started with some potential energy. The magnets are both on and at the same height when the algorithm begins. The algorithm is as follows, it can be tuned by changing the values A,B,C,D which are on the order of 500-600 milliseconds.<br /> <br /> Release magnet one<br /> Motor on counterclockwise for A milliseconds<br /> Motor off<br /> Magnet one on<br /> Release magnet two<br /> Motor on counterclockwise for B milliseconds<br /> Motor off<br /> Magnet two on<br /> Release magnet two<br /> Motor on clockwise for C milliseconds<br /> Motor off<br /> Magnet two on<br /> Release magnet one<br /> Motor on clockwise for D milliseconds<br /> Motor off<br /> Magnet one on<br /> <br /> This process is repeated, and overtime, the monkeybot climbs. A video of this can be found [http://www.youtube.com/watch?v=TA2VcH_GDJ0 here.]<br /> <br /> ==Mechanical Design==<br /> ===Parts List===<br /> The robot contains:<br /> <br /> Two acrylic links<br /> Two rotational ball-bearings<br /> Two [http://catalog.apwcompany.com/item/electromagnets/1-0-diameter-round-br-em100/em100-6-122?&amp;seo=110 electro-magnets]<br /> Two [http://www.usa.canon.com/html/industrial_encoders/lre_tr36.html rotary encoders]<br /> One [[Media:pittmangearmotor.pdf|Pittmann GM8224]] [[Actuators Available in the Mechatronics Lab |DC Motor]] with 19.5:1 Gear Head<br /> <br /> ===Design Considerations===<br /> The two links, made of 1/8” thick acrylic, create the body of the robot and create a mount for both bearings and the motor. The thickness and the material was chosen to minimize weight, and thus the torque required to swing the robot. The links were produced using a laser cutter. The rotational ball bearings mount on the links and hold the magnets, allowing the robot to swing around a fixed point. The encoders are mounted above the magnets on a bridge, so that they are capable of measuring the rotation of the link around the magnet.<br /> <br /> The Pittman motor was chosen to provide enough torque to the links to overcome friction. The gear head is also needed to get the necessary torque. With the gear head, the Pittmann is capable of providing 2.1 Nm of torque, which is more than enough for this application. However, the motor is rather large and thus increases the overall weight of the system.<br /> <br /> The data sheet for the Pittamnn motor can be found [[Media:pittmangearmotor.pdf|here]].<br /> <br /> ==Electrical Design==<br /> <br /> ==Code==<br /> <br /> ==Results and Reflections==<br /> We successfully created a climbing robot, however, the monkeybot was not as intelligent as we had originally hoped. It was unable to swing itself up from rest using a variety of closed loop control laws, most likely due to the large amounts of friction. To combat the high friction, we started the swinging link with some potential energy. From that point, it was relatively simple to design and tune an open loop time based algorithm which causes the robot to climb.<br /> <br /> A closed loop control system using encoders on both the magnets and the motor would improve this project. With this feedback, all of the necessary angles are known and thus the state of the robot is known at all times. If the robot knows its own position, it is better able to adjust to errors, such as a magnet slipping or variations in friction. An open loop time based algorithm can not adjust itself, as the timing of the sequence is hard coded.</div>

NathanHenry https://hades.mech.northwestern.edu//index.php?title=Monkeybot&diff=12676 2009-03-20T03:46:58Z

<p>NathanHenry: </p> <hr /> <div>[[Image:monkeybot_pic|thumb|right|350px|Moneybot Picture]]<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> <br /> ==Team Members==<br /> [[Image:Nathan_and_Nelson|thumb|right|200px|Nelson Rosa, Nathan Henry]]<br /> Nathan Henry - Senior, Mechanical Engineering&lt;br&gt;<br /> Nelson Rosa - Ph.D Student, Mechanical Engineering<br /> &lt;br clear=all&gt;<br /> <br /> ==Overview==<br /> The goal of this project was to create a brachiating robot capable of swinging itself side to side or climbing. This two link robot has [http://catalog.apwcompany.com/item/electromagnets/1-0-diameter-round-br-em100/em100-6-122?&amp;seo=110 electro-magnets] on each end and a [[Actuators Available in the Mechatronics Lab | DC motor]] at the pivot. With one magnet on, the robot swings under gravity and is aided by a input torque from the motor. This torque allows the swinging robot to overcome friction and pump energy into the system. Once the swinging arm has enough energy, the second magnet reaches a point at the same height or above the first magnet. At this point, the second magnet is turned on the motor is turned off. Now the process is repeated, swinging on the second magnet.<br /> <br /> We attempted to control the motor using both a closed loop control, with [http://www.usa.canon.com/html/industrial_encoders/lre_tr36.html rotary encoders], and an open loop control, using a time based algorithm.<br /> <br /> [http://www.youtube.com/watch?v=TA2VcH_GDJ0 Video of the monkeybot climbing]<br /> <br /> ==Geometry==<br /> [[Image:Monkeybot Geometry|thumb|left|200px|Monkeybot Geometry]]<br /> The monkeybot behaves like a double-pendulum system. The geometry, and our definitions of angles is shown to the right. The two angles important to us are the angle between the top link and a horizontal reference, and the angle between the two links. The rotary encoders over the magnet provide a measurement of the first angel, while the motor encoder measures the second.<br /> <br /> With these two angles we are able to implement a variety of control laws as described below. <br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> <br /> ==Control Method==<br /> <br /> ===Closed Loop Control===<br /> [[Image:Rotary_Encoder_TR_36|thumb|right|200px|Laser Rotary Encoder]]<br /> We first attempted to control the DC motor using feedback from a [http://www.usa.canon.com/html/industrial_encoders/lre_tr36.html rotary encoder] placed directly over each magnet. From this encoder, using both the A and B channels, we are able to determine the sign of the top link's velocity. We then implemented a simple control law in which the motor is full on in the same direction that the top link is rotating. This causes the lower link to pump in phase with the top link, mimicking the motion of a person on a swing set.<br /> <br /> With this control law we were able to pump energy into the system, however, we were never able to add enough energy to get the bottom magnet to a height equal to or above the top magnet. Starting from a resting position, with the lower link dangling straight down, the bottom link pumps in phase with the top link. The bottom magnet gradually gets higher and higher, but seems to stop increasing when it reaches a height slightly below the fixed magnet. Friction seems to be the main reason why the robot can not climb.<br /> <br /> We also implemented a control law where the lower link pumped out of phase with the top link. This caused a large increase in the movement of the top link, however, the bottom magnet stays in nearly the same position throughout.<br /> <br /> &lt;br&gt;<br /> &lt;br&gt;<br /> <br /> ===Open Loop Control===<br /> Our second approach was an open loop, time based algorithm. It involves no feedback and is just a simple set of commands implemented by the PIC. In order for the monkeybot to climb, the first link must be started with some potential energy. The magnets are both on and at the same height when the algorithm begins. The algorithm is as follows, it can be tuned by changing the values A,B,C,D which are on the order of 500-600 milliseconds.<br /> <br /> Release magnet one<br /> Motor on counterclockwise for A milliseconds<br /> Motor off<br /> Magnet one on<br /> Release magnet two<br /> Motor on counterclockwise for B milliseconds<br /> Motor off<br /> Magnet two on<br /> Release magnet two<br /> Motor on clockwise for C milliseconds<br /> Motor off<br /> Magnet two on<br /> Release magnet one<br /> Motor on clockwise for D milliseconds<br /> Motor off<br /> Magnet one on<br /> <br /> This process is repeated, and overtime, the monkeybot climbs. A video of this can be found [http://www.youtube.com/watch?v=TA2VcH_GDJ0 here.]<br /> <br /> ==Mechanical Design==<br /> ===Parts List===<br /> The robot contains:<br /> <br /> Two acrylic links<br /> Two rotational ball-bearings<br /> Two [http://catalog.apwcompany.com/item/electromagnets/1-0-diameter-round-br-em100/em100-6-122?&amp;seo=110 electro-magnets]<br /> Two [http://www.usa.canon.com/html/industrial_encoders/lre_tr36.html rotary encoders]<br /> One [[Media:pittmangearmotor.pdf|Pittmann GM8224]] [[Actuators Available in the Mechatronics Lab |DC Motor]] with 19.5:1 Gear Head<br /> <br /> ===Design Considerations===<br /> The two links, made of 1/8” thick acrylic, create the body of the robot and create a mount for both bearings and the motor. The thickness and the material was chosen to minimize weight, and thus the torque required to swing the robot. The links were produced using a laser cutter. The rotational ball bearings mount on the links and hold the magnets, allowing the robot to swing around a fixed point. The encoders are mounted above the magnets on a bridge, so that they are capable of measuring the rotation of the link around the magnet.<br /> <br /> The Pittman motor was chosen to provide enough torque to the links to overcome friction. The gear head is also needed to get the necessary torque. With the gear head, the Pittmann is capable of providing 2.1 Nm of torque, which is more than enough for this application. However, the motor is rather large and thus increases the overall weight of the system.<br /> <br /> The data sheet for the Pittamnn motor can be found [[Media:pittmangearmotor.pdf|here]].<br /> <br /> ==Electrical Design==<br /> <br /> ==Code==<br /> <br /> ==Results and Reflections==<br /> We successfully created a climbing robot, however, the monkeybot was not as intelligent as we had originally hoped. It was unable to swing itself up from rest using a variety of closed loop control laws, most likely due to the large amounts of friction. To combat the high friction, we started the swinging link with some potential energy. From that point, it was relatively simple to design and tune an open loop time based algorithm which causes the robot to climb.<br /> <br /> A closed loop control system using encoders on both the magnets and the motor would improve this project. With this feedback, all of the necessary angles are known and thus the state of the robot is known at all times. If the robot knows its own position, it is better able to adjust to errors, such as a magnet slipping or variations in friction. An open loop time based algorithm can not adjust itself, as the timing of the sequence is hard coded.</div>

NathanHenry https://hades.mech.northwestern.edu//index.php?title=Monkeybot&diff=12674 2009-03-20T03:46:27Z

<p>NathanHenry: </p> <hr /> <div>[[Image:monkeybot_pic|thumb|right|350px|Moneybot Picture]]<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> ==Team Members==<br /> [[Image:Nathan_and_Nelson|thumb|right|200px|Nelson Rosa, Nathan Henry]]<br /> Nathan Henry - Senior, Mechanical Engineering&lt;br&gt;<br /> Nelson Rosa - Ph.D Student, Mechanical Engineering<br /> &lt;br clear=all&gt;<br /> <br /> ==Overview==<br /> The goal of this project was to create a brachiating robot capable of swinging itself side to side or climbing. This two link robot has [http://catalog.apwcompany.com/item/electromagnets/1-0-diameter-round-br-em100/em100-6-122?&amp;seo=110 electro-magnets] on each end and a [[Actuators Available in the Mechatronics Lab | DC motor]] at the pivot. With one magnet on, the robot swings under gravity and is aided by a input torque from the motor. This torque allows the swinging robot to overcome friction and pump energy into the system. Once the swinging arm has enough energy, the second magnet reaches a point at the same height or above the first magnet. At this point, the second magnet is turned on the motor is turned off. Now the process is repeated, swinging on the second magnet.<br /> <br /> We attempted to control the motor using both a closed loop control, with [http://www.usa.canon.com/html/industrial_encoders/lre_tr36.html rotary encoders], and an open loop control, using a time based algorithm.<br /> <br /> [http://www.youtube.com/watch?v=TA2VcH_GDJ0 Video of the monkeybot climbing]<br /> <br /> ==Geometry==<br /> [[Image:Monkeybot Geometry|thumb|left|200px|Monkeybot Geometry]]<br /> The monkeybot behaves like a double-pendulum system. The geometry, and our definitions of angles is shown to the right. The two angles important to us are the angle between the top link and a horizontal reference, and the angle between the two links. The rotary encoders over the magnet provide a measurement of the first angel, while the motor encoder measures the second.<br /> <br /> With these two angles we are able to implement a variety of control laws as described below. <br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> <br /> ==Control Method==<br /> <br /> ===Closed Loop Control===<br /> [[Image:Rotary_Encoder_TR_36|thumb|right|200px|Laser Rotary Encoder]]<br /> We first attempted to control the DC motor using feedback from a [http://www.usa.canon.com/html/industrial_encoders/lre_tr36.html rotary encoder] placed directly over each magnet. From this encoder, using both the A and B channels, we are able to determine the sign of the top link's velocity. We then implemented a simple control law in which the motor is full on in the same direction that the top link is rotating. This causes the lower link to pump in phase with the top link, mimicking the motion of a person on a swing set.<br /> <br /> With this control law we were able to pump energy into the system, however, we were never able to add enough energy to get the bottom magnet to a height equal to or above the top magnet. Starting from a resting position, with the lower link dangling straight down, the bottom link pumps in phase with the top link. The bottom magnet gradually gets higher and higher, but seems to stop increasing when it reaches a height slightly below the fixed magnet. Friction seems to be the main reason why the robot can not climb.<br /> <br /> We also implemented a control law where the lower link pumped out of phase with the top link. This caused a large increase in the movement of the top link, however, the bottom magnet stays in nearly the same position throughout.<br /> <br /> &lt;br&gt;<br /> &lt;br&gt;<br /> <br /> ===Open Loop Control===<br /> Our second approach was an open loop, time based algorithm. It involves no feedback and is just a simple set of commands implemented by the PIC. In order for the monkeybot to climb, the first link must be started with some potential energy. The magnets are both on and at the same height when the algorithm begins. The algorithm is as follows, it can be tuned by changing the values A,B,C,D which are on the order of 500-600 milliseconds.<br /> <br /> Release magnet one<br /> Motor on counterclockwise for A milliseconds<br /> Motor off<br /> Magnet one on<br /> Release magnet two<br /> Motor on counterclockwise for B milliseconds<br /> Motor off<br /> Magnet two on<br /> Release magnet two<br /> Motor on clockwise for C milliseconds<br /> Motor off<br /> Magnet two on<br /> Release magnet one<br /> Motor on clockwise for D milliseconds<br /> Motor off<br /> Magnet one on<br /> <br /> This process is repeated, and overtime, the monkeybot climbs. A video of this can be found [http://www.youtube.com/watch?v=TA2VcH_GDJ0 here.]<br /> <br /> ==Mechanical Design==<br /> ===Parts List===<br /> The robot contains:<br /> <br /> Two acrylic links<br /> Two rotational ball-bearings<br /> Two [http://catalog.apwcompany.com/item/electromagnets/1-0-diameter-round-br-em100/em100-6-122?&amp;seo=110 electro-magnets]<br /> Two [http://www.usa.canon.com/html/industrial_encoders/lre_tr36.html rotary encoders]<br /> One [[Media:pittmangearmotor.pdf|Pittmann GM8224]] [[Actuators Available in the Mechatronics Lab |DC Motor]] with 19.5:1 Gear Head<br /> <br /> ===Design Considerations===<br /> The two links, made of 1/8” thick acrylic, create the body of the robot and create a mount for both bearings and the motor. The thickness and the material was chosen to minimize weight, and thus the torque required to swing the robot. The links were produced using a laser cutter. The rotational ball bearings mount on the links and hold the magnets, allowing the robot to swing around a fixed point. The encoders are mounted above the magnets on a bridge, so that they are capable of measuring the rotation of the link around the magnet.<br /> <br /> The Pittman motor was chosen to provide enough torque to the links to overcome friction. The gear head is also needed to get the necessary torque. With the gear head, the Pittmann is capable of providing 2.1 Nm of torque, which is more than enough for this application. However, the motor is rather large and thus increases the overall weight of the system.<br /> <br /> The data sheet for the Pittamnn motor can be found [[Media:pittmangearmotor.pdf|here]].<br /> <br /> ==Electrical Design==<br /> <br /> ==Code==<br /> <br /> ==Results and Reflections==<br /> We successfully created a climbing robot, however, the monkeybot was not as intelligent as we had originally hoped. It was unable to swing itself up from rest using a variety of closed loop control laws, most likely due to the large amounts of friction. To combat the high friction, we started the swinging link with some potential energy. From that point, it was relatively simple to design and tune an open loop time based algorithm which causes the robot to climb.<br /> <br /> A closed loop control system using encoders on both the magnets and the motor would improve this project. With this feedback, all of the necessary angles are known and thus the state of the robot is known at all times. If the robot knows its own position, it is better able to adjust to errors, such as a magnet slipping or variations in friction. An open loop time based algorithm can not adjust itself, as the timing of the sequence is hard coded.</div>

NathanHenry https://hades.mech.northwestern.edu//index.php?title=Monkeybot&diff=12672 2009-03-20T03:45:36Z

<p>NathanHenry: </p> <hr /> <div>[[Image:monkeybot_pic|thumb|right|350px|Moneybot Picture]]<br /> &lt;br clear=all&gt;<br /> ==Team Members==<br /> [[Image:Nathan_and_Nelson|thumb|right|200px|Nelson Rosa, Nathan Henry]]<br /> Nathan Henry - Senior, Mechanical Engineering&lt;br&gt;<br /> Nelson Rosa - Ph.D Student, Mechanical Engineering<br /> &lt;br clear=all&gt;<br /> <br /> ==Overview==<br /> The goal of this project was to create a brachiating robot capable of swinging itself side to side or climbing. This two link robot has [http://catalog.apwcompany.com/item/electromagnets/1-0-diameter-round-br-em100/em100-6-122?&amp;seo=110 electro-magnets] on each end and a [[Actuators Available in the Mechatronics Lab | DC motor]] at the pivot. With one magnet on, the robot swings under gravity and is aided by a input torque from the motor. This torque allows the swinging robot to overcome friction and pump energy into the system. Once the swinging arm has enough energy, the second magnet reaches a point at the same height or above the first magnet. At this point, the second magnet is turned on the motor is turned off. Now the process is repeated, swinging on the second magnet.<br /> <br /> We attempted to control the motor using both a closed loop control, with [http://www.usa.canon.com/html/industrial_encoders/lre_tr36.html rotary encoders], and an open loop control, using a time based algorithm.<br /> <br /> [http://www.youtube.com/watch?v=TA2VcH_GDJ0 Video of the monkeybot climbing]<br /> <br /> ==Geometry==<br /> [[Image:Monkeybot Geometry|thumb|left|200px|Monkeybot Geometry]]<br /> The monkeybot behaves like a double-pendulum system. The geometry, and our definitions of angles is shown to the right. The two angles important to us are the angle between the top link and a horizontal reference, and the angle between the two links. The rotary encoders over the magnet provide a measurement of the first angel, while the motor encoder measures the second.<br /> <br /> With these two angles we are able to implement a variety of control laws as described below. <br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> <br /> ==Control Method==<br /> <br /> ===Closed Loop Control===<br /> [[Image:Rotary_Encoder_TR_36|thumb|right|200px|Laser Rotary Encoder]]<br /> We first attempted to control the DC motor using feedback from a [http://www.usa.canon.com/html/industrial_encoders/lre_tr36.html rotary encoder] placed directly over each magnet. From this encoder, using both the A and B channels, we are able to determine the sign of the top link's velocity. We then implemented a simple control law in which the motor is full on in the same direction that the top link is rotating. This causes the lower link to pump in phase with the top link, mimicking the motion of a person on a swing set.<br /> <br /> With this control law we were able to pump energy into the system, however, we were never able to add enough energy to get the bottom magnet to a height equal to or above the top magnet. Starting from a resting position, with the lower link dangling straight down, the bottom link pumps in phase with the top link. The bottom magnet gradually gets higher and higher, but seems to stop increasing when it reaches a height slightly below the fixed magnet. Friction seems to be the main reason why the robot can not climb.<br /> <br /> We also implemented a control law where the lower link pumped out of phase with the top link. This caused a large increase in the movement of the top link, however, the bottom magnet stays in nearly the same position throughout.<br /> <br /> &lt;br&gt;<br /> &lt;br&gt;<br /> <br /> ===Open Loop Control===<br /> Our second approach was an open loop, time based algorithm. It involves no feedback and is just a simple set of commands implemented by the PIC. In order for the monkeybot to climb, the first link must be started with some potential energy. The magnets are both on and at the same height when the algorithm begins. The algorithm is as follows, it can be tuned by changing the values A,B,C,D which are on the order of 500-600 milliseconds.<br /> <br /> Release magnet one<br /> Motor on counterclockwise for A milliseconds<br /> Motor off<br /> Magnet one on<br /> Release magnet two<br /> Motor on counterclockwise for B milliseconds<br /> Motor off<br /> Magnet two on<br /> Release magnet two<br /> Motor on clockwise for C milliseconds<br /> Motor off<br /> Magnet two on<br /> Release magnet one<br /> Motor on clockwise for D milliseconds<br /> Motor off<br /> Magnet one on<br /> <br /> This process is repeated, and overtime, the monkeybot climbs. A video of this can be found [http://www.youtube.com/watch?v=TA2VcH_GDJ0 here.]<br /> <br /> ==Mechanical Design==<br /> ===Parts List===<br /> The robot contains:<br /> <br /> Two acrylic links<br /> Two rotational ball-bearings<br /> Two [http://catalog.apwcompany.com/item/electromagnets/1-0-diameter-round-br-em100/em100-6-122?&amp;seo=110 electro-magnets]<br /> Two [http://www.usa.canon.com/html/industrial_encoders/lre_tr36.html rotary encoders]<br /> One [[Media:pittmangearmotor.pdf|Pittmann GM8224]] [[Actuators Available in the Mechatronics Lab |DC Motor]] with 19.5:1 Gear Head<br /> <br /> ===Design Considerations===<br /> The two links, made of 1/8” thick acrylic, create the body of the robot and create a mount for both bearings and the motor. The thickness and the material was chosen to minimize weight, and thus the torque required to swing the robot. The links were produced using a laser cutter. The rotational ball bearings mount on the links and hold the magnets, allowing the robot to swing around a fixed point. The encoders are mounted above the magnets on a bridge, so that they are capable of measuring the rotation of the link around the magnet.<br /> <br /> The Pittman motor was chosen to provide enough torque to the links to overcome friction. The gear head is also needed to get the necessary torque. With the gear head, the Pittmann is capable of providing 2.1 Nm of torque, which is more than enough for this application. However, the motor is rather large and thus increases the overall weight of the system.<br /> <br /> The data sheet for the Pittamnn motor can be found [[Media:pittmangearmotor.pdf|here]].<br /> <br /> ==Electrical Design==<br /> <br /> ==Code==<br /> <br /> ==Results and Reflections==<br /> We successfully created a climbing robot, however, the monkeybot was not as intelligent as we had originally hoped. It was unable to swing itself up from rest using a variety of closed loop control laws, most likely due to the large amounts of friction. To combat the high friction, we started the swinging link with some potential energy. From that point, it was relatively simple to design and tune an open loop time based algorithm which causes the robot to climb.<br /> <br /> A closed loop control system using encoders on both the magnets and the motor would improve this project. With this feedback, all of the necessary angles are known and thus the state of the robot is known at all times. If the robot knows its own position, it is better able to adjust to errors, such as a magnet slipping or variations in friction. An open loop time based algorithm can not adjust itself, as the timing of the sequence is hard coded.</div>

NathanHenry https://hades.mech.northwestern.edu//index.php?title=ME_333_final_projects&diff=12671 2009-03-20T03:44:45Z

<p>NathanHenry: /* Monkeybot */</p> <hr /> <div>See the '''[[ME 333 end of course schedule]]'''. <br /> <br /> Final projects for ME 333 in years 2000-2007 can be found<br /> '''[http://lims.mech.northwestern.edu/~design/mechatronics/ here]'''.<br /> <br /> __TOC__<br /> <br /> <br /> == ME 333 Final Projects 2009 ==<br /> <br /> === [[Mozart's Right Hand]] ===<br /> [[Image:mrh_box.JPG|thumb|150px|Mozart's Right Hand|right]]<br /> Mozart's Right Hand is a musical instrument capable of playing two full octaves of the [http://en.wikipedia.org/wiki/Diatonic_scale Diatonic Scale.] The user wears a glove on his right hand and uses motions of the hand and fingers to create different notes that are played with a speaker. The pitch of the note is controlled by the orientation of the user's hand as he rotates it ether from the wrist, the elbow, or the shoulder. The LCD on the front of the box tells the user the pitch that corresponds to his or her current hand orientation. When the user touches together his thumb and index finger, the speaker plays the tone. A [http://www.youtube.com/watch?v=vec-W4QeHQU video] of Mozart's Right Hand in action is available on YouTube.<br /> <br /> <br /> &lt;br clear=all&gt;<br /> <br /> === [[Persistence-of-Vision Display]] ===<br /> <br /> &lt;br clear=all&gt;<br /> === [[Rock Paper Scissors Machine]] ===<br /> [[Image:rps whole thing.JPG|thumb|150px|Rock Paper Scissors Machine|right]]<br /> &lt;br clear=all&gt;<br /> <br /> === [[Three-speaker Chladni Patterns]] ===<br /> [[Image:chladni_660hz|right|thumb|150px]]<br /> This project uses three speakers to generate shapes on a circular aluminum plate depending on which frequency the speakers are playing at. Once the speakers hit a resonant frequency of the plate, salt migrates to the nodes (zero amplitude) regions of the plate to form distinct patterns.<br /> &lt;br clear=all&gt;<br /> <br /> === [[Basketball]] ===<br /> [[Image:Mechatronics2009Bball|right|thumb|150px]]<br /> This project consists of a throwing arm propelled by a Pittman motor is mounted on a turntable and throws the ball into the &quot;hoop.&quot; The hoop is wrapped in reflective tape and an IR emitter, receiver pair is used to sense where the IR is reflected most (the hoop with highly reflective tape). An ultrasonic sensor then pings the hoop for the distance of the hoop. With this information, the arm is able to &quot;make a basket.&quot;<br /> &lt;br clear=all&gt;<br /> <br /> === [[Robot Drummer]] ===<br /> [[Image:Robot_Drummer.jpg|thumb|400pix|right|Robot Drummer]]<br /> The Robot Drummer is a device that demonstrates high-speed motor control by being able to drum when given commands. Through an RS232 cable, Matlab sends commands to a &quot;master&quot; PIC. The master then sends the commands to two &quot;slave&quot; PICs through I2C communication. The slaves take the commands and implement PID control of the motors.<br /> &lt;br clear=all&gt;<br /> <br /> === [[Automated Fish Refuge]] ===<br /> [[Image:Entire Fish Refuge|right|thumb|200px]]<br /> The automated fish refuge allows for the controlled movement of a fish refuge with the goal of recording specific behavior. The mechanical design is completely adjustable and allows adjustable degrees of oscillating movement and orientation of the refuge. The program is primarily in MATLAB for ease of use and the velocity profile can be a sine, square, triangle, or any function that the user inputs. [http://www.youtube.com/watch?v=wGOKujMhN88 Check out the video!]<br /> <br /> &lt;br clear=all&gt;<br /> <br /> === [[Marionette]] ===<br /> <br /> &lt;br clear=all&gt;<br /> === [[Monkeybot]] ===<br /> [[Image:monkeybot_pic|thumb|right|200px|Moneybot]]<br /> The monkeybot, is a swinging robot capable of moving side to side and climbing. It consists of a two link, double pendulum system with an electro-magnet on each end. At the pivot is a DC motor, which provides an input torque and allows the swinging system to gain energy and climb. Check out the video of the monkeybot climbing [http://www.youtube.com/watch?v=TA2VcH_GDJ0 here]. <br /> &lt;br clear=all&gt;<br /> <br /> === [[PPOD-mini: 6-DOF Shaker]] ===<br /> [[Image:PPOD_mini.JPG|thumb|200x200 px|right|PPOD-mini 6-DOF Shaker]]<br /> The PPOD-mini is a miniaturized version of the Programmable Part-feeding Oscillatory Device ([http://lims.mech.northwestern.edu/projects/frictioninducedforcefields/index.htm PPOD]) found in the Laboratory for Intelligent Mechanical Systems (LIMS) at Northwestern. The PPOD-mini utilizes six speakers that act like actuators. The speakers are connected to a acrylic plate via flexures of tygon and iron. In its current implementation, the phase of the speakers can be controlled independently, giving the device six degrees of freedom. The movement of objects placed on the acrylic plate can be controlled by changing the phases of the speakers.<br /> <br /> <br /> &lt;br clear=all&gt;<br /> <br /> === [[Automated Xylophone]] ===<br /> [[Image:AutomatedXylophonePicture1.jpg|thumb|200x200 px|right|Automated Xylophone]]<br /> The Automated Xylophone controls several solenoids which hit various pitches on an actual xylophone based on the note selected. The device has two main modes: using the keypad, a user can choose to either play notes in real time or store songs to be played back later. A video of the Automated Xylophone playing in real time mode can be found [http://www.youtube.com/watch?v=_ubpAEyq9kg here].<br /> <br /> <br /> &lt;br clear=all&gt;<br /> <br /> === [[Vision-based Cannon]] ===<br /> [[Image:SM_Gun_Camera_PIC_Setup.JPG|thumb|200x200 px|right|Vision-based Cannon]]<br /> This project uses a webcam and Matlab to analyze an image and direct a modified USB Missile Launcher to fire at targets found in the image.<br /> <br /> &lt;br clear=all&gt;<br /> <br /> == ME 333 Final Projects 2008 ==<br /> <br /> === [[IR Tracker]] ===<br /> <br /> [[Image:IR_Tracker_Main.jpg|right|thumb|200px]]<br /> <br /> The IR Tracker (aka &quot;Spot&quot;) is a device that follows a moving infrared light. It continuously detects the position of an infrared emitter in two axes, and then tracks the emitter with a laser. [[Media:MT_MS_AZ_TrackerVideo.mp4|See Spot Run.]]<br /> <br /> '''Chosen the OUTSTANDING PROJECT by the students of ME 333.'''<br /> <br /> &lt;br clear=all&gt;<br /> <br /> === [[Robot Snake]] ===<br /> [[Image:HLSSnakeMain.jpg|right|thumb|200px]]<br /> <br /> This remote control robotic snake uses servo motors with a traveling sine wave motion profile to mimic serpentine motion. The robotic snake is capable of moving forward, left, right and in reverse. <br /> [http://www.youtube.com/watch?v=r_GOOFLnI6w Video of the robot snake]<br /> <br /> &lt;br clear=all&gt;<br /> <br /> === [[Programmable Stiffness Joint]] === <br /> <br /> [[Image:SteelToePic2.jpg|thumb|200px|The 'Steel Toe' programmable stiffness joint|right]]<br /> <br /> The Programmable Stiffness Joint varies rotational stiffness as desired by the user. It is the first step in modeling the mechanical impedance of the human ankle joint (both stiffness and damping) for the purpose of determining the respective breakdown of the two properties over the gait cycle.<br /> <br /> &lt;br clear=all&gt;<br /> <br /> <br /> === [[Magnetic based sample purification]] ===<br /> <br /> <br /> &lt;br clear=all&gt;<br /> <br /> <br /> === [[Continuously Variable Transmission]] ===<br /> <br /> [[image:CVT_system.JPG|thumb|200px]]<br /> <br /> This prototype is a proof of concept model of a variable ratio transmission to be implemented in the 2008-2009 Formula SAE competition vehicle. The gear ratio is determined by the distances between the pulley halves which are controllable electronically. <br /> <br /> &lt;br clear=all&gt;<br /> <br /> === [[Granular Flow Rotating Sphere]] ===<br /> [[Image:Team-21-main-picture.JPG|right|thumb|200px]]<br /> This device will be used to study the granular flow of particles within a rotating sphere. The sphere is filled with grains of varying size and then rotated about two different axes according to a series of position and angular velocity inputs.<br /> <br /> &lt;br clear=all&gt;<br /> <br /> === [[Vibratory Clock]] ===<br /> <br /> [[Image:Vibratory_Clock.jpg|right|thumb|Vibratory Clock|200px]]<br /> <br /> The Vibratory Clock allows a small object to act as an hour &quot;hand&quot; on a horizontal circular platform that is actuated from underneath by three speakers. The object slides around the circular platform, impelled by friction forces due to the vibration. [http://www.youtube.com/watch?v=KhgTNCfdwZw Check it out!]<br /> <br /> &lt;br clear=all&gt;<br /> <br /> === [[WiiMouse]] ===<br /> <br /> [[Image:HPIM1027.jpg|right|thumb|200px]]<br /> <br /> The WiiMouse is a handheld remote that can be used to move a cursor on a windows-based PC, via accelerometer input captured through device movement.<br /> <br /> &lt;br clear=all&gt;<br /> <br /> === [[Intelligent Oscillation Controller]] ===<br /> <br /> [[image:ME333_learning_oscillator.jpg|thumb|200px]]<br /> <br /> This device &quot;learns&quot; a forcing function that is applied to a spring and mass system to match an arbitrary, periodic acceleration profile.<br /> <br /> &lt;br clear=all&gt;<br /> <br /> === [[Baseball]] ===<br /> <br /> [[Image:Baseball_Playfield.jpg|Sweet Baseball Game|right|thumb|200px]]<br /> <br /> An interactive baseball game inspired by pinball, featuring pitching, batting, light up bases and a scoreboard to keep track of the game.<br /> <br /> &lt;br clear=all&gt;<br /> <br /> === [[Ball Balancing Challenge]] ===<br /> <br /> [[Image:Ballbalancechallenge.JPG|right|thumb|200px]]<br /> <br /> An interactive game involving ball balancing on a touchscreen with touchscreen feedback and joystick action. <br /> <br /> &lt;br clear=all&gt;</div>

NathanHenry https://hades.mech.northwestern.edu//index.php?title=ME_333_final_projects&diff=12670 2009-03-20T03:43:57Z

<p>NathanHenry: /* Monkeybot */</p> <hr /> <div>See the '''[[ME 333 end of course schedule]]'''. <br /> <br /> Final projects for ME 333 in years 2000-2007 can be found<br /> '''[http://lims.mech.northwestern.edu/~design/mechatronics/ here]'''.<br /> <br /> __TOC__<br /> <br /> <br /> == ME 333 Final Projects 2009 ==<br /> <br /> === [[Mozart's Right Hand]] ===<br /> [[Image:mrh_box.JPG|thumb|150px|Mozart's Right Hand|right]]<br /> Mozart's Right Hand is a musical instrument capable of playing two full octaves of the [http://en.wikipedia.org/wiki/Diatonic_scale Diatonic Scale.] The user wears a glove on his right hand and uses motions of the hand and fingers to create different notes that are played with a speaker. The pitch of the note is controlled by the orientation of the user's hand as he rotates it ether from the wrist, the elbow, or the shoulder. The LCD on the front of the box tells the user the pitch that corresponds to his or her current hand orientation. When the user touches together his thumb and index finger, the speaker plays the tone. A [http://www.youtube.com/watch?v=vec-W4QeHQU video] of Mozart's Right Hand in action is available on YouTube.<br /> <br /> <br /> &lt;br clear=all&gt;<br /> <br /> === [[Persistence-of-Vision Display]] ===<br /> <br /> &lt;br clear=all&gt;<br /> === [[Rock Paper Scissors Machine]] ===<br /> [[Image:rps whole thing.JPG|thumb|150px|Rock Paper Scissors Machine|right]]<br /> &lt;br clear=all&gt;<br /> <br /> === [[Three-speaker Chladni Patterns]] ===<br /> [[Image:chladni_660hz|right|thumb|150px]]<br /> This project uses three speakers to generate shapes on a circular aluminum plate depending on which frequency the speakers are playing at. Once the speakers hit a resonant frequency of the plate, salt migrates to the nodes (zero amplitude) regions of the plate to form distinct patterns.<br /> &lt;br clear=all&gt;<br /> <br /> === [[Basketball]] ===<br /> [[Image:Mechatronics2009Bball|right|thumb|150px]]<br /> This project consists of a throwing arm propelled by a Pittman motor is mounted on a turntable and throws the ball into the &quot;hoop.&quot; The hoop is wrapped in reflective tape and an IR emitter, receiver pair is used to sense where the IR is reflected most (the hoop with highly reflective tape). An ultrasonic sensor then pings the hoop for the distance of the hoop. With this information, the arm is able to &quot;make a basket.&quot;<br /> &lt;br clear=all&gt;<br /> <br /> === [[Robot Drummer]] ===<br /> [[Image:Robot_Drummer.jpg|thumb|400pix|right|Robot Drummer]]<br /> The Robot Drummer is a device that demonstrates high-speed motor control by being able to drum when given commands. Through an RS232 cable, Matlab sends commands to a &quot;master&quot; PIC. The master then sends the commands to two &quot;slave&quot; PICs through I2C communication. The slaves take the commands and implement PID control of the motors.<br /> &lt;br clear=all&gt;<br /> <br /> === [[Automated Fish Refuge]] ===<br /> [[Image:Entire Fish Refuge|right|thumb|200px]]<br /> The automated fish refuge allows for the controlled movement of a fish refuge with the goal of recording specific behavior. The mechanical design is completely adjustable and allows adjustable degrees of oscillating movement and orientation of the refuge. The program is primarily in MATLAB for ease of use and the velocity profile can be a sine, square, triangle, or any function that the user inputs. [http://www.youtube.com/watch?v=wGOKujMhN88 Check out the video!]<br /> <br /> &lt;br clear=all&gt;<br /> <br /> === [[Marionette]] ===<br /> <br /> &lt;br clear=all&gt;<br /> === [[Monkeybot]] ===<br /> [[Image:monkeybot_pic|thumb|right|200px|Moneybot]]<br /> The monkeybot, is a swinging robot capable of moving side to side and climbing. It consists of a two link, double pendulum system with a electro-magnet on each end. At the pivot is a DC motor, which provides an input torque and allows the swinging system to gain energy and climb. Check out the video of the monkeybot climbing [http://www.youtube.com/watch?v=TA2VcH_GDJ0 here]. <br /> &lt;br clear=all&gt;<br /> <br /> === [[PPOD-mini: 6-DOF Shaker]] ===<br /> [[Image:PPOD_mini.JPG|thumb|200x200 px|right|PPOD-mini 6-DOF Shaker]]<br /> The PPOD-mini is a miniaturized version of the Programmable Part-feeding Oscillatory Device ([http://lims.mech.northwestern.edu/projects/frictioninducedforcefields/index.htm PPOD]) found in the Laboratory for Intelligent Mechanical Systems (LIMS) at Northwestern. The PPOD-mini utilizes six speakers that act like actuators. The speakers are connected to a acrylic plate via flexures of tygon and iron. In its current implementation, the phase of the speakers can be controlled independently, giving the device six degrees of freedom. The movement of objects placed on the acrylic plate can be controlled by changing the phases of the speakers.<br /> <br /> <br /> &lt;br clear=all&gt;<br /> <br /> === [[Automated Xylophone]] ===<br /> [[Image:AutomatedXylophonePicture1.jpg|thumb|200x200 px|right|Automated Xylophone]]<br /> The Automated Xylophone controls several solenoids which hit various pitches on an actual xylophone based on the note selected. The device has two main modes: using the keypad, a user can choose to either play notes in real time or store songs to be played back later. A video of the Automated Xylophone playing in real time mode can be found [http://www.youtube.com/watch?v=_ubpAEyq9kg here].<br /> <br /> <br /> &lt;br clear=all&gt;<br /> <br /> === [[Vision-based Cannon]] ===<br /> [[Image:SM_Gun_Camera_PIC_Setup.JPG|thumb|200x200 px|right|Vision-based Cannon]]<br /> This project uses a webcam and Matlab to analyze an image and direct a modified USB Missile Launcher to fire at targets found in the image.<br /> <br /> &lt;br clear=all&gt;<br /> <br /> == ME 333 Final Projects 2008 ==<br /> <br /> === [[IR Tracker]] ===<br /> <br /> [[Image:IR_Tracker_Main.jpg|right|thumb|200px]]<br /> <br /> The IR Tracker (aka &quot;Spot&quot;) is a device that follows a moving infrared light. It continuously detects the position of an infrared emitter in two axes, and then tracks the emitter with a laser. [[Media:MT_MS_AZ_TrackerVideo.mp4|See Spot Run.]]<br /> <br /> '''Chosen the OUTSTANDING PROJECT by the students of ME 333.'''<br /> <br /> &lt;br clear=all&gt;<br /> <br /> === [[Robot Snake]] ===<br /> [[Image:HLSSnakeMain.jpg|right|thumb|200px]]<br /> <br /> This remote control robotic snake uses servo motors with a traveling sine wave motion profile to mimic serpentine motion. The robotic snake is capable of moving forward, left, right and in reverse. <br /> [http://www.youtube.com/watch?v=r_GOOFLnI6w Video of the robot snake]<br /> <br /> &lt;br clear=all&gt;<br /> <br /> === [[Programmable Stiffness Joint]] === <br /> <br /> [[Image:SteelToePic2.jpg|thumb|200px|The 'Steel Toe' programmable stiffness joint|right]]<br /> <br /> The Programmable Stiffness Joint varies rotational stiffness as desired by the user. It is the first step in modeling the mechanical impedance of the human ankle joint (both stiffness and damping) for the purpose of determining the respective breakdown of the two properties over the gait cycle.<br /> <br /> &lt;br clear=all&gt;<br /> <br /> <br /> === [[Magnetic based sample purification]] ===<br /> <br /> <br /> &lt;br clear=all&gt;<br /> <br /> <br /> === [[Continuously Variable Transmission]] ===<br /> <br /> [[image:CVT_system.JPG|thumb|200px]]<br /> <br /> This prototype is a proof of concept model of a variable ratio transmission to be implemented in the 2008-2009 Formula SAE competition vehicle. The gear ratio is determined by the distances between the pulley halves which are controllable electronically. <br /> <br /> &lt;br clear=all&gt;<br /> <br /> === [[Granular Flow Rotating Sphere]] ===<br /> [[Image:Team-21-main-picture.JPG|right|thumb|200px]]<br /> This device will be used to study the granular flow of particles within a rotating sphere. The sphere is filled with grains of varying size and then rotated about two different axes according to a series of position and angular velocity inputs.<br /> <br /> &lt;br clear=all&gt;<br /> <br /> === [[Vibratory Clock]] ===<br /> <br /> [[Image:Vibratory_Clock.jpg|right|thumb|Vibratory Clock|200px]]<br /> <br /> The Vibratory Clock allows a small object to act as an hour &quot;hand&quot; on a horizontal circular platform that is actuated from underneath by three speakers. The object slides around the circular platform, impelled by friction forces due to the vibration. [http://www.youtube.com/watch?v=KhgTNCfdwZw Check it out!]<br /> <br /> &lt;br clear=all&gt;<br /> <br /> === [[WiiMouse]] ===<br /> <br /> [[Image:HPIM1027.jpg|right|thumb|200px]]<br /> <br /> The WiiMouse is a handheld remote that can be used to move a cursor on a windows-based PC, via accelerometer input captured through device movement.<br /> <br /> &lt;br clear=all&gt;<br /> <br /> === [[Intelligent Oscillation Controller]] ===<br /> <br /> [[image:ME333_learning_oscillator.jpg|thumb|200px]]<br /> <br /> This device &quot;learns&quot; a forcing function that is applied to a spring and mass system to match an arbitrary, periodic acceleration profile.<br /> <br /> &lt;br clear=all&gt;<br /> <br /> === [[Baseball]] ===<br /> <br /> [[Image:Baseball_Playfield.jpg|Sweet Baseball Game|right|thumb|200px]]<br /> <br /> An interactive baseball game inspired by pinball, featuring pitching, batting, light up bases and a scoreboard to keep track of the game.<br /> <br /> &lt;br clear=all&gt;<br /> <br /> === [[Ball Balancing Challenge]] ===<br /> <br /> [[Image:Ballbalancechallenge.JPG|right|thumb|200px]]<br /> <br /> An interactive game involving ball balancing on a touchscreen with touchscreen feedback and joystick action. <br /> <br /> &lt;br clear=all&gt;</div>

NathanHenry https://hades.mech.northwestern.edu//index.php?title=ME_333_final_projects&diff=12668 2009-03-20T03:43:17Z

<p>NathanHenry: /* Monkeybot */</p> <hr /> <div>See the '''[[ME 333 end of course schedule]]'''. <br /> <br /> Final projects for ME 333 in years 2000-2007 can be found<br /> '''[http://lims.mech.northwestern.edu/~design/mechatronics/ here]'''.<br /> <br /> __TOC__<br /> <br /> <br /> == ME 333 Final Projects 2009 ==<br /> <br /> === [[Mozart's Right Hand]] ===<br /> [[Image:mrh_box.JPG|thumb|150px|Mozart's Right Hand|right]]<br /> Mozart's Right Hand is a musical instrument capable of playing two full octaves of the [http://en.wikipedia.org/wiki/Diatonic_scale Diatonic Scale.] The user wears a glove on his right hand and uses motions of the hand and fingers to create different notes that are played with a speaker. The pitch of the note is controlled by the orientation of the user's hand as he rotates it ether from the wrist, the elbow, or the shoulder. The LCD on the front of the box tells the user the pitch that corresponds to his or her current hand orientation. When the user touches together his thumb and index finger, the speaker plays the tone. A [http://www.youtube.com/watch?v=vec-W4QeHQU video] of Mozart's Right Hand in action is available on YouTube.<br /> <br /> <br /> &lt;br clear=all&gt;<br /> <br /> === [[Persistence-of-Vision Display]] ===<br /> <br /> &lt;br clear=all&gt;<br /> === [[Rock Paper Scissors Machine]] ===<br /> [[Image:rps whole thing.JPG|thumb|150px|Rock Paper Scissors Machine|right]]<br /> &lt;br clear=all&gt;<br /> <br /> === [[Three-speaker Chladni Patterns]] ===<br /> [[Image:chladni_660hz|right|thumb|150px]]<br /> This project uses three speakers to generate shapes on a circular aluminum plate depending on which frequency the speakers are playing at. Once the speakers hit a resonant frequency of the plate, salt migrates to the nodes (zero amplitude) regions of the plate to form distinct patterns.<br /> &lt;br clear=all&gt;<br /> <br /> === [[Basketball]] ===<br /> [[Image:Mechatronics2009Bball|right|thumb|150px]]<br /> This project consists of a throwing arm propelled by a Pittman motor is mounted on a turntable and throws the ball into the &quot;hoop.&quot; The hoop is wrapped in reflective tape and an IR emitter, receiver pair is used to sense where the IR is reflected most (the hoop with highly reflective tape). An ultrasonic sensor then pings the hoop for the distance of the hoop. With this information, the arm is able to &quot;make a basket.&quot;<br /> &lt;br clear=all&gt;<br /> <br /> === [[Robot Drummer]] ===<br /> [[Image:Robot_Drummer.jpg|thumb|400pix|right|Robot Drummer]]<br /> The Robot Drummer is a device that demonstrates high-speed motor control by being able to drum when given commands. Through an RS232 cable, Matlab sends commands to a &quot;master&quot; PIC. The master then sends the commands to two &quot;slave&quot; PICs through I2C communication. The slaves take the commands and implement PID control of the motors.<br /> &lt;br clear=all&gt;<br /> <br /> === [[Automated Fish Refuge]] ===<br /> [[Image:Entire Fish Refuge|right|thumb|200px]]<br /> The automated fish refuge allows for the controlled movement of a fish refuge with the goal of recording specific behavior. The mechanical design is completely adjustable and allows adjustable degrees of oscillating movement and orientation of the refuge. The program is primarily in MATLAB for ease of use and the velocity profile can be a sine, square, triangle, or any function that the user inputs. [http://www.youtube.com/watch?v=wGOKujMhN88 Check out the video!]<br /> <br /> &lt;br clear=all&gt;<br /> <br /> === [[Marionette]] ===<br /> <br /> &lt;br clear=all&gt;<br /> === [[Monkeybot]] ===<br /> [[Image:monkeybot_pic|thumb|right|200px|Moneybot]]<br /> The monkeybot, is a swinging robot capable of moving side to side and climbing. It consists of a two link, double pendulum system with a electro-magnet on each end. At the pivot is a DC motor, which provides an input torque and allows the swinging system to gain energy and climb. Check out the video of the monkeybot climbing [[http://www.youtube.com/watch?v=TA2VcH_GDJ0 here]]. <br /> &lt;br clear=all&gt;<br /> <br /> === [[PPOD-mini: 6-DOF Shaker]] ===<br /> [[Image:PPOD_mini.JPG|thumb|200x200 px|right|PPOD-mini 6-DOF Shaker]]<br /> The PPOD-mini is a miniaturized version of the Programmable Part-feeding Oscillatory Device ([http://lims.mech.northwestern.edu/projects/frictioninducedforcefields/index.htm PPOD]) found in the Laboratory for Intelligent Mechanical Systems (LIMS) at Northwestern. The PPOD-mini utilizes six speakers that act like actuators. The speakers are connected to a acrylic plate via flexures of tygon and iron. In its current implementation, the phase of the speakers can be controlled independently, giving the device six degrees of freedom. The movement of objects placed on the acrylic plate can be controlled by changing the phases of the speakers.<br /> <br /> <br /> &lt;br clear=all&gt;<br /> <br /> === [[Automated Xylophone]] ===<br /> [[Image:AutomatedXylophonePicture1.jpg|thumb|200x200 px|right|Automated Xylophone]]<br /> The Automated Xylophone controls several solenoids which hit various pitches on an actual xylophone based on the note selected. The device has two main modes: using the keypad, a user can choose to either play notes in real time or store songs to be played back later. A video of the Automated Xylophone playing in real time mode can be found [http://www.youtube.com/watch?v=_ubpAEyq9kg here].<br /> <br /> <br /> &lt;br clear=all&gt;<br /> <br /> === [[Vision-based Cannon]] ===<br /> [[Image:SM_Gun_Camera_PIC_Setup.JPG|thumb|200x200 px|right|Vision-based Cannon]]<br /> This project uses a webcam and Matlab to analyze an image and direct a modified USB Missile Launcher to fire at targets found in the image.<br /> <br /> &lt;br clear=all&gt;<br /> <br /> == ME 333 Final Projects 2008 ==<br /> <br /> === [[IR Tracker]] ===<br /> <br /> [[Image:IR_Tracker_Main.jpg|right|thumb|200px]]<br /> <br /> The IR Tracker (aka &quot;Spot&quot;) is a device that follows a moving infrared light. It continuously detects the position of an infrared emitter in two axes, and then tracks the emitter with a laser. [[Media:MT_MS_AZ_TrackerVideo.mp4|See Spot Run.]]<br /> <br /> '''Chosen the OUTSTANDING PROJECT by the students of ME 333.'''<br /> <br /> &lt;br clear=all&gt;<br /> <br /> === [[Robot Snake]] ===<br /> [[Image:HLSSnakeMain.jpg|right|thumb|200px]]<br /> <br /> This remote control robotic snake uses servo motors with a traveling sine wave motion profile to mimic serpentine motion. The robotic snake is capable of moving forward, left, right and in reverse. <br /> [http://www.youtube.com/watch?v=r_GOOFLnI6w Video of the robot snake]<br /> <br /> &lt;br clear=all&gt;<br /> <br /> === [[Programmable Stiffness Joint]] === <br /> <br /> [[Image:SteelToePic2.jpg|thumb|200px|The 'Steel Toe' programmable stiffness joint|right]]<br /> <br /> The Programmable Stiffness Joint varies rotational stiffness as desired by the user. It is the first step in modeling the mechanical impedance of the human ankle joint (both stiffness and damping) for the purpose of determining the respective breakdown of the two properties over the gait cycle.<br /> <br /> &lt;br clear=all&gt;<br /> <br /> <br /> === [[Magnetic based sample purification]] ===<br /> <br /> <br /> &lt;br clear=all&gt;<br /> <br /> <br /> === [[Continuously Variable Transmission]] ===<br /> <br /> [[image:CVT_system.JPG|thumb|200px]]<br /> <br /> This prototype is a proof of concept model of a variable ratio transmission to be implemented in the 2008-2009 Formula SAE competition vehicle. The gear ratio is determined by the distances between the pulley halves which are controllable electronically. <br /> <br /> &lt;br clear=all&gt;<br /> <br /> === [[Granular Flow Rotating Sphere]] ===<br /> [[Image:Team-21-main-picture.JPG|right|thumb|200px]]<br /> This device will be used to study the granular flow of particles within a rotating sphere. The sphere is filled with grains of varying size and then rotated about two different axes according to a series of position and angular velocity inputs.<br /> <br /> &lt;br clear=all&gt;<br /> <br /> === [[Vibratory Clock]] ===<br /> <br /> [[Image:Vibratory_Clock.jpg|right|thumb|Vibratory Clock|200px]]<br /> <br /> The Vibratory Clock allows a small object to act as an hour &quot;hand&quot; on a horizontal circular platform that is actuated from underneath by three speakers. The object slides around the circular platform, impelled by friction forces due to the vibration. [http://www.youtube.com/watch?v=KhgTNCfdwZw Check it out!]<br /> <br /> &lt;br clear=all&gt;<br /> <br /> === [[WiiMouse]] ===<br /> <br /> [[Image:HPIM1027.jpg|right|thumb|200px]]<br /> <br /> The WiiMouse is a handheld remote that can be used to move a cursor on a windows-based PC, via accelerometer input captured through device movement.<br /> <br /> &lt;br clear=all&gt;<br /> <br /> === [[Intelligent Oscillation Controller]] ===<br /> <br /> [[image:ME333_learning_oscillator.jpg|thumb|200px]]<br /> <br /> This device &quot;learns&quot; a forcing function that is applied to a spring and mass system to match an arbitrary, periodic acceleration profile.<br /> <br /> &lt;br clear=all&gt;<br /> <br /> === [[Baseball]] ===<br /> <br /> [[Image:Baseball_Playfield.jpg|Sweet Baseball Game|right|thumb|200px]]<br /> <br /> An interactive baseball game inspired by pinball, featuring pitching, batting, light up bases and a scoreboard to keep track of the game.<br /> <br /> &lt;br clear=all&gt;<br /> <br /> === [[Ball Balancing Challenge]] ===<br /> <br /> [[Image:Ballbalancechallenge.JPG|right|thumb|200px]]<br /> <br /> An interactive game involving ball balancing on a touchscreen with touchscreen feedback and joystick action. <br /> <br /> &lt;br clear=all&gt;</div>

NathanHenry https://hades.mech.northwestern.edu//index.php?title=Monkeybot&diff=12655 2009-03-20T03:38:02Z

<p>NathanHenry: /* Parts List */</p> <hr /> <div>[[Image:monkeybot_pic|thumb|right|350px|Moneybot Picture]]<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> ==Team Members==<br /> [[Image:Nathan_and_Nelson|thumb|right|200px|Nelson Rosa, Nathan Henry]]<br /> Nathan Henry - Senior, Mechanical Engineering&lt;br&gt;<br /> Nelson Rosa - Ph.D Student, Mechanical Engineering<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> <br /> ==Overview==<br /> The goal of this project was to create a brachiating robot capable of swinging itself side to side or climbing. This two link robot has [http://catalog.apwcompany.com/item/electromagnets/1-0-diameter-round-br-em100/em100-6-122?&amp;seo=110 electro-magnets] on each end and a [[Actuators Available in the Mechatronics Lab | DC motor]] at the pivot. With one magnet on, the robot swings under gravity and is aided by a input torque from the motor. This torque allows the swinging robot to overcome friction and pump energy into the system. Once the swinging arm has enough energy, the second magnet reaches a point at the same height or above the first magnet. At this point, the second magnet is turned on the motor is turned off. Now the process is repeated, swinging on the second magnet.<br /> <br /> We attempted to control the motor using both a closed loop control, with [http://www.usa.canon.com/html/industrial_encoders/lre_tr36.html rotary encoders], and an open loop control, using a time based algorithm.<br /> <br /> [http://www.youtube.com/watch?v=TA2VcH_GDJ0 Video of the monkeybot climbing]<br /> <br /> ==Geometry==<br /> [[Image:Monkeybot Geometry|thumb|left|200px|Monkeybot Geometry]]<br /> The monkeybot behaves like a double-pendulum system. The geometry, and our definitions of angles is shown to the right. The two angles important to us are the angle between the top link and a horizontal reference, and the angle between the two links. The rotary encoders over the magnet provide a measurement of the first angel, while the motor encoder measures the second.<br /> <br /> With these two angles we are able to implement a variety of control laws as described below. <br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> <br /> ==Control Method==<br /> <br /> ===Closed Loop Control===<br /> [[Image:Rotary_Encoder_TR_36|thumb|right|200px|Laser Rotary Encoder]]<br /> We first attempted to control the DC motor using feedback from a [http://www.usa.canon.com/html/industrial_encoders/lre_tr36.html rotary encoder] placed directly over each magnet. From this encoder, using both the A and B channels, we are able to determine the sign of the top link's velocity. We then implemented a simple control law in which the motor is full on in the same direction that the top link is rotating. This causes the lower link to pump in phase with the top link, mimicking the motion of a person on a swing set.<br /> <br /> With this control law we were able to pump energy into the system, however, we were never able to add enough energy to get the bottom magnet to a height equal to or above the top magnet. Starting from a resting position, with the lower link dangling straight down, the bottom link pumps in phase with the top link. The bottom magnet gradually gets higher and higher, but seems to stop increasing when it reaches a height slightly below the fixed magnet. Friction seems to be the main reason why the robot can not climb.<br /> <br /> We also implemented a control law where the lower link pumped out of phase with the top link. This caused a large increase in the movement of the top link, however, the bottom magnet stays in nearly the same position throughout.<br /> <br /> &lt;br&gt;<br /> &lt;br&gt;<br /> <br /> ===Open Loop Control===<br /> Our second approach was an open loop, time based algorithm. It involves no feedback and is just a simple set of commands implemented by the PIC. In order for the monkeybot to climb, the first link must be started with some potential energy. The magnets are both on and at the same height when the algorithm begins. The algorithm is as follows, it can be tuned by changing the values A,B,C,D which are on the order of 500-600 milliseconds.<br /> <br /> Release magnet one<br /> Motor on counterclockwise for A milliseconds<br /> Motor off<br /> Magnet one on<br /> Release magnet two<br /> Motor on counterclockwise for B milliseconds<br /> Motor off<br /> Magnet two on<br /> Release magnet two<br /> Motor on clockwise for C milliseconds<br /> Motor off<br /> Magnet two on<br /> Release magnet one<br /> Motor on clockwise for D milliseconds<br /> Motor off<br /> Magnet one on<br /> <br /> This process is repeated, and overtime, the monkeybot climbs. A video of this can be found [http://www.youtube.com/watch?v=TA2VcH_GDJ0 here.]<br /> <br /> ==Mechanical Design==<br /> ===Parts List===<br /> The robot contains:<br /> <br /> Two acrylic links<br /> Two rotational ball-bearings<br /> Two [http://catalog.apwcompany.com/item/electromagnets/1-0-diameter-round-br-em100/em100-6-122?&amp;seo=110 electro-magnets]<br /> Two [http://www.usa.canon.com/html/industrial_encoders/lre_tr36.html rotary encoders]<br /> One [[Media:pittmangearmotor.pdf|Pittmann GM8224]] [[Actuators Available in the Mechatronics Lab |DC Motor]] with 19.5:1 Gear Head<br /> <br /> ===Design Considerations===<br /> The two links, made of 1/8” thick acrylic, create the body of the robot and create a mount for both bearings and the motor. The thickness and the material was chosen to minimize weight, and thus the torque required to swing the robot. The links were produced using a laser cutter. The rotational ball bearings mount on the links and hold the magnets, allowing the robot to swing around a fixed point. The encoders are mounted above the magnets on a bridge, so that they are capable of measuring the rotation of the link around the magnet.<br /> <br /> The Pittman motor was chosen to provide enough torque to the links to overcome friction. The gear head is also needed to get the necessary torque. With the gear head, the Pittmann is capable of providing 2.1 Nm of torque, which is more than enough for this application. However, the motor is rather large and thus increases the overall weight of the system.<br /> <br /> The data sheet for the Pittamnn motor can be found [[Media:pittmangearmotor.pdf|here]].<br /> <br /> ==Electrical Design==<br /> <br /> ==Code==<br /> <br /> ==Results and Reflections==<br /> We successfully created a climbing robot, however, the monkeybot was not as intelligent as we had originally hoped. It was unable to swing itself up from rest using a variety of closed loop control laws, most likely due to the large amounts of friction. To combat the high friction, we started the swinging link with some potential energy. From that point, it was relatively simple to design and tune an open loop time based algorithm which causes the robot to climb.<br /> <br /> A closed loop control system using encoders on both the magnets and the motor would improve this project. With this feedback, all of the necessary angles are known and thus the state of the robot is known at all times. If the robot knows its own position, it is better able to adjust to errors, such as a magnet slipping or variations in friction. An open loop time based algorithm can not adjust itself, as the timing of the sequence is hard coded.</div>

NathanHenry https://hades.mech.northwestern.edu//index.php?title=Monkeybot&diff=12654 2009-03-20T03:37:11Z

<p>NathanHenry: /* Design Considerations */</p> <hr /> <div>[[Image:monkeybot_pic|thumb|right|350px|Moneybot Picture]]<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> ==Team Members==<br /> [[Image:Nathan_and_Nelson|thumb|right|200px|Nelson Rosa, Nathan Henry]]<br /> Nathan Henry - Senior, Mechanical Engineering&lt;br&gt;<br /> Nelson Rosa - Ph.D Student, Mechanical Engineering<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> <br /> ==Overview==<br /> The goal of this project was to create a brachiating robot capable of swinging itself side to side or climbing. This two link robot has [http://catalog.apwcompany.com/item/electromagnets/1-0-diameter-round-br-em100/em100-6-122?&amp;seo=110 electro-magnets] on each end and a [[Actuators Available in the Mechatronics Lab | DC motor]] at the pivot. With one magnet on, the robot swings under gravity and is aided by a input torque from the motor. This torque allows the swinging robot to overcome friction and pump energy into the system. Once the swinging arm has enough energy, the second magnet reaches a point at the same height or above the first magnet. At this point, the second magnet is turned on the motor is turned off. Now the process is repeated, swinging on the second magnet.<br /> <br /> We attempted to control the motor using both a closed loop control, with [http://www.usa.canon.com/html/industrial_encoders/lre_tr36.html rotary encoders], and an open loop control, using a time based algorithm.<br /> <br /> [http://www.youtube.com/watch?v=TA2VcH_GDJ0 Video of the monkeybot climbing]<br /> <br /> ==Geometry==<br /> [[Image:Monkeybot Geometry|thumb|left|200px|Monkeybot Geometry]]<br /> The monkeybot behaves like a double-pendulum system. The geometry, and our definitions of angles is shown to the right. The two angles important to us are the angle between the top link and a horizontal reference, and the angle between the two links. The rotary encoders over the magnet provide a measurement of the first angel, while the motor encoder measures the second.<br /> <br /> With these two angles we are able to implement a variety of control laws as described below. <br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> <br /> ==Control Method==<br /> <br /> ===Closed Loop Control===<br /> [[Image:Rotary_Encoder_TR_36|thumb|right|200px|Laser Rotary Encoder]]<br /> We first attempted to control the DC motor using feedback from a [http://www.usa.canon.com/html/industrial_encoders/lre_tr36.html rotary encoder] placed directly over each magnet. From this encoder, using both the A and B channels, we are able to determine the sign of the top link's velocity. We then implemented a simple control law in which the motor is full on in the same direction that the top link is rotating. This causes the lower link to pump in phase with the top link, mimicking the motion of a person on a swing set.<br /> <br /> With this control law we were able to pump energy into the system, however, we were never able to add enough energy to get the bottom magnet to a height equal to or above the top magnet. Starting from a resting position, with the lower link dangling straight down, the bottom link pumps in phase with the top link. The bottom magnet gradually gets higher and higher, but seems to stop increasing when it reaches a height slightly below the fixed magnet. Friction seems to be the main reason why the robot can not climb.<br /> <br /> We also implemented a control law where the lower link pumped out of phase with the top link. This caused a large increase in the movement of the top link, however, the bottom magnet stays in nearly the same position throughout.<br /> <br /> &lt;br&gt;<br /> &lt;br&gt;<br /> <br /> ===Open Loop Control===<br /> Our second approach was an open loop, time based algorithm. It involves no feedback and is just a simple set of commands implemented by the PIC. In order for the monkeybot to climb, the first link must be started with some potential energy. The magnets are both on and at the same height when the algorithm begins. The algorithm is as follows, it can be tuned by changing the values A,B,C,D which are on the order of 500-600 milliseconds.<br /> <br /> Release magnet one<br /> Motor on counterclockwise for A milliseconds<br /> Motor off<br /> Magnet one on<br /> Release magnet two<br /> Motor on counterclockwise for B milliseconds<br /> Motor off<br /> Magnet two on<br /> Release magnet two<br /> Motor on clockwise for C milliseconds<br /> Motor off<br /> Magnet two on<br /> Release magnet one<br /> Motor on clockwise for D milliseconds<br /> Motor off<br /> Magnet one on<br /> <br /> This process is repeated, and overtime, the monkeybot climbs. A video of this can be found [http://www.youtube.com/watch?v=TA2VcH_GDJ0 here.]<br /> <br /> ==Mechanical Design==<br /> ===Parts List===<br /> The robot contains:<br /> <br /> Two acrylic links<br /> Two rotational ball-bearings<br /> Two [http://catalog.apwcompany.com/item/electromagnets/1-0-diameter-round-br-em100/em100-6-122?&amp;seo=110 electro-magnets]<br /> Two [http://www.usa.canon.com/html/industrial_encoders/lre_tr36.html rotary encoders]<br /> One Pittman GM8224 [[Actuators Available in the Mechatronics Lab |DC Motor]] with 19.5:1 Gear Head<br /> <br /> ===Design Considerations===<br /> The two links, made of 1/8” thick acrylic, create the body of the robot and create a mount for both bearings and the motor. The thickness and the material was chosen to minimize weight, and thus the torque required to swing the robot. The links were produced using a laser cutter. The rotational ball bearings mount on the links and hold the magnets, allowing the robot to swing around a fixed point. The encoders are mounted above the magnets on a bridge, so that they are capable of measuring the rotation of the link around the magnet.<br /> <br /> The Pittman motor was chosen to provide enough torque to the links to overcome friction. The gear head is also needed to get the necessary torque. With the gear head, the Pittmann is capable of providing 2.1 Nm of torque, which is more than enough for this application. However, the motor is rather large and thus increases the overall weight of the system.<br /> <br /> The data sheet for the Pittamnn motor can be found [[Media:pittmangearmotor.pdf|here]].<br /> <br /> ==Electrical Design==<br /> <br /> ==Code==<br /> <br /> ==Results and Reflections==<br /> We successfully created a climbing robot, however, the monkeybot was not as intelligent as we had originally hoped. It was unable to swing itself up from rest using a variety of closed loop control laws, most likely due to the large amounts of friction. To combat the high friction, we started the swinging link with some potential energy. From that point, it was relatively simple to design and tune an open loop time based algorithm which causes the robot to climb.<br /> <br /> A closed loop control system using encoders on both the magnets and the motor would improve this project. With this feedback, all of the necessary angles are known and thus the state of the robot is known at all times. If the robot knows its own position, it is better able to adjust to errors, such as a magnet slipping or variations in friction. An open loop time based algorithm can not adjust itself, as the timing of the sequence is hard coded.</div>

NathanHenry https://hades.mech.northwestern.edu//index.php?title=Monkeybot&diff=12648 2009-03-20T03:34:58Z

<p>NathanHenry: /* Parts List */</p> <hr /> <div>[[Image:monkeybot_pic|thumb|right|350px|Moneybot Picture]]<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> ==Team Members==<br /> [[Image:Nathan_and_Nelson|thumb|right|200px|Nelson Rosa, Nathan Henry]]<br /> Nathan Henry - Senior, Mechanical Engineering&lt;br&gt;<br /> Nelson Rosa - Ph.D Student, Mechanical Engineering<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> <br /> ==Overview==<br /> The goal of this project was to create a brachiating robot capable of swinging itself side to side or climbing. This two link robot has [http://catalog.apwcompany.com/item/electromagnets/1-0-diameter-round-br-em100/em100-6-122?&amp;seo=110 electro-magnets] on each end and a [[Actuators Available in the Mechatronics Lab | DC motor]] at the pivot. With one magnet on, the robot swings under gravity and is aided by a input torque from the motor. This torque allows the swinging robot to overcome friction and pump energy into the system. Once the swinging arm has enough energy, the second magnet reaches a point at the same height or above the first magnet. At this point, the second magnet is turned on the motor is turned off. Now the process is repeated, swinging on the second magnet.<br /> <br /> We attempted to control the motor using both a closed loop control, with [http://www.usa.canon.com/html/industrial_encoders/lre_tr36.html rotary encoders], and an open loop control, using a time based algorithm.<br /> <br /> [http://www.youtube.com/watch?v=TA2VcH_GDJ0 Video of the monkeybot climbing]<br /> <br /> ==Geometry==<br /> [[Image:Monkeybot Geometry|thumb|left|200px|Monkeybot Geometry]]<br /> The monkeybot behaves like a double-pendulum system. The geometry, and our definitions of angles is shown to the right. The two angles important to us are the angle between the top link and a horizontal reference, and the angle between the two links. The rotary encoders over the magnet provide a measurement of the first angel, while the motor encoder measures the second.<br /> <br /> With these two angles we are able to implement a variety of control laws as described below. <br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> <br /> ==Control Method==<br /> <br /> ===Closed Loop Control===<br /> [[Image:Rotary_Encoder_TR_36|thumb|right|200px|Laser Rotary Encoder]]<br /> We first attempted to control the DC motor using feedback from a [http://www.usa.canon.com/html/industrial_encoders/lre_tr36.html rotary encoder] placed directly over each magnet. From this encoder, using both the A and B channels, we are able to determine the sign of the top link's velocity. We then implemented a simple control law in which the motor is full on in the same direction that the top link is rotating. This causes the lower link to pump in phase with the top link, mimicking the motion of a person on a swing set.<br /> <br /> With this control law we were able to pump energy into the system, however, we were never able to add enough energy to get the bottom magnet to a height equal to or above the top magnet. Starting from a resting position, with the lower link dangling straight down, the bottom link pumps in phase with the top link. The bottom magnet gradually gets higher and higher, but seems to stop increasing when it reaches a height slightly below the fixed magnet. Friction seems to be the main reason why the robot can not climb.<br /> <br /> We also implemented a control law where the lower link pumped out of phase with the top link. This caused a large increase in the movement of the top link, however, the bottom magnet stays in nearly the same position throughout.<br /> <br /> &lt;br&gt;<br /> &lt;br&gt;<br /> <br /> ===Open Loop Control===<br /> Our second approach was an open loop, time based algorithm. It involves no feedback and is just a simple set of commands implemented by the PIC. In order for the monkeybot to climb, the first link must be started with some potential energy. The magnets are both on and at the same height when the algorithm begins. The algorithm is as follows, it can be tuned by changing the values A,B,C,D which are on the order of 500-600 milliseconds.<br /> <br /> Release magnet one<br /> Motor on counterclockwise for A milliseconds<br /> Motor off<br /> Magnet one on<br /> Release magnet two<br /> Motor on counterclockwise for B milliseconds<br /> Motor off<br /> Magnet two on<br /> Release magnet two<br /> Motor on clockwise for C milliseconds<br /> Motor off<br /> Magnet two on<br /> Release magnet one<br /> Motor on clockwise for D milliseconds<br /> Motor off<br /> Magnet one on<br /> <br /> This process is repeated, and overtime, the monkeybot climbs. A video of this can be found [http://www.youtube.com/watch?v=TA2VcH_GDJ0 here.]<br /> <br /> ==Mechanical Design==<br /> ===Parts List===<br /> The robot contains:<br /> <br /> Two acrylic links<br /> Two rotational ball-bearings<br /> Two [http://catalog.apwcompany.com/item/electromagnets/1-0-diameter-round-br-em100/em100-6-122?&amp;seo=110 electro-magnets]<br /> Two [http://www.usa.canon.com/html/industrial_encoders/lre_tr36.html rotary encoders]<br /> One Pittman GM8224 [[Actuators Available in the Mechatronics Lab |DC Motor]] with 19.5:1 Gear Head<br /> <br /> ===Design Considerations===<br /> The two links, made of 1/8” thick acrylic, create the body of the robot and create a mount for both bearings and the motor. The thickness and the material was chosen to minimize weight, and thus the torque required to swing the robot. The links were produced using a laser cutter. The rotational ball bearings mount on the links and hold the magnets, allowing the robot to swing around a fixed point. The encoders are mounted above the magnets on a bridge, so that they are capable of measuring the rotation of the link around the magnet.<br /> <br /> The Pittman motor was chosen to provide enough torque to the links to overcome friction. The gear head is also needed to get the necessary torque. With the gear head, the Pittmann is capable of providing 2.1 Nm of torque, which is more than enough for this application. However, the motor is rather large and thus increases the overall weight of the system.<br /> <br /> ==Electrical Design==<br /> <br /> ==Code==<br /> <br /> ==Results and Reflections==<br /> We successfully created a climbing robot, however, the monkeybot was not as intelligent as we had originally hoped. It was unable to swing itself up from rest using a variety of closed loop control laws, most likely due to the large amounts of friction. To combat the high friction, we started the swinging link with some potential energy. From that point, it was relatively simple to design and tune an open loop time based algorithm which causes the robot to climb.<br /> <br /> A closed loop control system using encoders on both the magnets and the motor would improve this project. With this feedback, all of the necessary angles are known and thus the state of the robot is known at all times. If the robot knows its own position, it is better able to adjust to errors, such as a magnet slipping or variations in friction. An open loop time based algorithm can not adjust itself, as the timing of the sequence is hard coded.</div>

NathanHenry https://hades.mech.northwestern.edu//index.php?title=Monkeybot&diff=12646 2009-03-20T03:34:34Z

<p>NathanHenry: /* Parts List */</p> <hr /> <div>[[Image:monkeybot_pic|thumb|right|350px|Moneybot Picture]]<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> ==Team Members==<br /> [[Image:Nathan_and_Nelson|thumb|right|200px|Nelson Rosa, Nathan Henry]]<br /> Nathan Henry - Senior, Mechanical Engineering&lt;br&gt;<br /> Nelson Rosa - Ph.D Student, Mechanical Engineering<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> <br /> ==Overview==<br /> The goal of this project was to create a brachiating robot capable of swinging itself side to side or climbing. This two link robot has [http://catalog.apwcompany.com/item/electromagnets/1-0-diameter-round-br-em100/em100-6-122?&amp;seo=110 electro-magnets] on each end and a [[Actuators Available in the Mechatronics Lab | DC motor]] at the pivot. With one magnet on, the robot swings under gravity and is aided by a input torque from the motor. This torque allows the swinging robot to overcome friction and pump energy into the system. Once the swinging arm has enough energy, the second magnet reaches a point at the same height or above the first magnet. At this point, the second magnet is turned on the motor is turned off. Now the process is repeated, swinging on the second magnet.<br /> <br /> We attempted to control the motor using both a closed loop control, with [http://www.usa.canon.com/html/industrial_encoders/lre_tr36.html rotary encoders], and an open loop control, using a time based algorithm.<br /> <br /> [http://www.youtube.com/watch?v=TA2VcH_GDJ0 Video of the monkeybot climbing]<br /> <br /> ==Geometry==<br /> [[Image:Monkeybot Geometry|thumb|left|200px|Monkeybot Geometry]]<br /> The monkeybot behaves like a double-pendulum system. The geometry, and our definitions of angles is shown to the right. The two angles important to us are the angle between the top link and a horizontal reference, and the angle between the two links. The rotary encoders over the magnet provide a measurement of the first angel, while the motor encoder measures the second.<br /> <br /> With these two angles we are able to implement a variety of control laws as described below. <br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> <br /> ==Control Method==<br /> <br /> ===Closed Loop Control===<br /> [[Image:Rotary_Encoder_TR_36|thumb|right|200px|Laser Rotary Encoder]]<br /> We first attempted to control the DC motor using feedback from a [http://www.usa.canon.com/html/industrial_encoders/lre_tr36.html rotary encoder] placed directly over each magnet. From this encoder, using both the A and B channels, we are able to determine the sign of the top link's velocity. We then implemented a simple control law in which the motor is full on in the same direction that the top link is rotating. This causes the lower link to pump in phase with the top link, mimicking the motion of a person on a swing set.<br /> <br /> With this control law we were able to pump energy into the system, however, we were never able to add enough energy to get the bottom magnet to a height equal to or above the top magnet. Starting from a resting position, with the lower link dangling straight down, the bottom link pumps in phase with the top link. The bottom magnet gradually gets higher and higher, but seems to stop increasing when it reaches a height slightly below the fixed magnet. Friction seems to be the main reason why the robot can not climb.<br /> <br /> We also implemented a control law where the lower link pumped out of phase with the top link. This caused a large increase in the movement of the top link, however, the bottom magnet stays in nearly the same position throughout.<br /> <br /> &lt;br&gt;<br /> &lt;br&gt;<br /> <br /> ===Open Loop Control===<br /> Our second approach was an open loop, time based algorithm. It involves no feedback and is just a simple set of commands implemented by the PIC. In order for the monkeybot to climb, the first link must be started with some potential energy. The magnets are both on and at the same height when the algorithm begins. The algorithm is as follows, it can be tuned by changing the values A,B,C,D which are on the order of 500-600 milliseconds.<br /> <br /> Release magnet one<br /> Motor on counterclockwise for A milliseconds<br /> Motor off<br /> Magnet one on<br /> Release magnet two<br /> Motor on counterclockwise for B milliseconds<br /> Motor off<br /> Magnet two on<br /> Release magnet two<br /> Motor on clockwise for C milliseconds<br /> Motor off<br /> Magnet two on<br /> Release magnet one<br /> Motor on clockwise for D milliseconds<br /> Motor off<br /> Magnet one on<br /> <br /> This process is repeated, and overtime, the monkeybot climbs. A video of this can be found [http://www.youtube.com/watch?v=TA2VcH_GDJ0 here.]<br /> <br /> ==Mechanical Design==<br /> ===Parts List===<br /> The robot contains:<br /> <br /> Two acrylic links<br /> Two rotational ball-bearings<br /> Two [http://catalog.apwcompany.com/item/electromagnets/1-0-diameter-round-br-em100/em100-6-122?&amp;seo=110 electro-magnets]<br /> Two [http://www.usa.canon.com/html/industrial_encoders/lre_tr36.html rotary encoders]<br /> One Pittman GM8224 [[Actuators Available in the Mechtronics Lab | DC Motor]] with 19.5:1 Gear Head<br /> <br /> ===Design Considerations===<br /> The two links, made of 1/8” thick acrylic, create the body of the robot and create a mount for both bearings and the motor. The thickness and the material was chosen to minimize weight, and thus the torque required to swing the robot. The links were produced using a laser cutter. The rotational ball bearings mount on the links and hold the magnets, allowing the robot to swing around a fixed point. The encoders are mounted above the magnets on a bridge, so that they are capable of measuring the rotation of the link around the magnet.<br /> <br /> The Pittman motor was chosen to provide enough torque to the links to overcome friction. The gear head is also needed to get the necessary torque. With the gear head, the Pittmann is capable of providing 2.1 Nm of torque, which is more than enough for this application. However, the motor is rather large and thus increases the overall weight of the system.<br /> <br /> ==Electrical Design==<br /> <br /> ==Code==<br /> <br /> ==Results and Reflections==<br /> We successfully created a climbing robot, however, the monkeybot was not as intelligent as we had originally hoped. It was unable to swing itself up from rest using a variety of closed loop control laws, most likely due to the large amounts of friction. To combat the high friction, we started the swinging link with some potential energy. From that point, it was relatively simple to design and tune an open loop time based algorithm which causes the robot to climb.<br /> <br /> A closed loop control system using encoders on both the magnets and the motor would improve this project. With this feedback, all of the necessary angles are known and thus the state of the robot is known at all times. If the robot knows its own position, it is better able to adjust to errors, such as a magnet slipping or variations in friction. An open loop time based algorithm can not adjust itself, as the timing of the sequence is hard coded.</div>

NathanHenry https://hades.mech.northwestern.edu//index.php?title=Monkeybot&diff=12644 2009-03-20T03:33:47Z

<p>NathanHenry: /* Overview */</p> <hr /> <div>[[Image:monkeybot_pic|thumb|right|350px|Moneybot Picture]]<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> ==Team Members==<br /> [[Image:Nathan_and_Nelson|thumb|right|200px|Nelson Rosa, Nathan Henry]]<br /> Nathan Henry - Senior, Mechanical Engineering&lt;br&gt;<br /> Nelson Rosa - Ph.D Student, Mechanical Engineering<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> <br /> ==Overview==<br /> The goal of this project was to create a brachiating robot capable of swinging itself side to side or climbing. This two link robot has [http://catalog.apwcompany.com/item/electromagnets/1-0-diameter-round-br-em100/em100-6-122?&amp;seo=110 electro-magnets] on each end and a [[Actuators Available in the Mechatronics Lab | DC motor]] at the pivot. With one magnet on, the robot swings under gravity and is aided by a input torque from the motor. This torque allows the swinging robot to overcome friction and pump energy into the system. Once the swinging arm has enough energy, the second magnet reaches a point at the same height or above the first magnet. At this point, the second magnet is turned on the motor is turned off. Now the process is repeated, swinging on the second magnet.<br /> <br /> We attempted to control the motor using both a closed loop control, with [http://www.usa.canon.com/html/industrial_encoders/lre_tr36.html rotary encoders], and an open loop control, using a time based algorithm.<br /> <br /> [http://www.youtube.com/watch?v=TA2VcH_GDJ0 Video of the monkeybot climbing]<br /> <br /> ==Geometry==<br /> [[Image:Monkeybot Geometry|thumb|left|200px|Monkeybot Geometry]]<br /> The monkeybot behaves like a double-pendulum system. The geometry, and our definitions of angles is shown to the right. The two angles important to us are the angle between the top link and a horizontal reference, and the angle between the two links. The rotary encoders over the magnet provide a measurement of the first angel, while the motor encoder measures the second.<br /> <br /> With these two angles we are able to implement a variety of control laws as described below. <br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> <br /> ==Control Method==<br /> <br /> ===Closed Loop Control===<br /> [[Image:Rotary_Encoder_TR_36|thumb|right|200px|Laser Rotary Encoder]]<br /> We first attempted to control the DC motor using feedback from a [http://www.usa.canon.com/html/industrial_encoders/lre_tr36.html rotary encoder] placed directly over each magnet. From this encoder, using both the A and B channels, we are able to determine the sign of the top link's velocity. We then implemented a simple control law in which the motor is full on in the same direction that the top link is rotating. This causes the lower link to pump in phase with the top link, mimicking the motion of a person on a swing set.<br /> <br /> With this control law we were able to pump energy into the system, however, we were never able to add enough energy to get the bottom magnet to a height equal to or above the top magnet. Starting from a resting position, with the lower link dangling straight down, the bottom link pumps in phase with the top link. The bottom magnet gradually gets higher and higher, but seems to stop increasing when it reaches a height slightly below the fixed magnet. Friction seems to be the main reason why the robot can not climb.<br /> <br /> We also implemented a control law where the lower link pumped out of phase with the top link. This caused a large increase in the movement of the top link, however, the bottom magnet stays in nearly the same position throughout.<br /> <br /> &lt;br&gt;<br /> &lt;br&gt;<br /> <br /> ===Open Loop Control===<br /> Our second approach was an open loop, time based algorithm. It involves no feedback and is just a simple set of commands implemented by the PIC. In order for the monkeybot to climb, the first link must be started with some potential energy. The magnets are both on and at the same height when the algorithm begins. The algorithm is as follows, it can be tuned by changing the values A,B,C,D which are on the order of 500-600 milliseconds.<br /> <br /> Release magnet one<br /> Motor on counterclockwise for A milliseconds<br /> Motor off<br /> Magnet one on<br /> Release magnet two<br /> Motor on counterclockwise for B milliseconds<br /> Motor off<br /> Magnet two on<br /> Release magnet two<br /> Motor on clockwise for C milliseconds<br /> Motor off<br /> Magnet two on<br /> Release magnet one<br /> Motor on clockwise for D milliseconds<br /> Motor off<br /> Magnet one on<br /> <br /> This process is repeated, and overtime, the monkeybot climbs. A video of this can be found [http://www.youtube.com/watch?v=TA2VcH_GDJ0 here.]<br /> <br /> ==Mechanical Design==<br /> ===Parts List===<br /> The robot contains:<br /> <br /> Two acrylic links<br /> Two rotational ball-bearings<br /> Two [http://catalog.apwcompany.com/item/electromagnets/1-0-diameter-round-br-em100/em100-6-122?&amp;seo=110 electro-magnets]<br /> Two [http://www.usa.canon.com/html/industrial_encoders/lre_tr36.html rotary encoders]<br /> One Pittman GM8224 DC Motor with 19.5:1 Gear Head<br /> <br /> ===Design Considerations===<br /> The two links, made of 1/8” thick acrylic, create the body of the robot and create a mount for both bearings and the motor. The thickness and the material was chosen to minimize weight, and thus the torque required to swing the robot. The links were produced using a laser cutter. The rotational ball bearings mount on the links and hold the magnets, allowing the robot to swing around a fixed point. The encoders are mounted above the magnets on a bridge, so that they are capable of measuring the rotation of the link around the magnet.<br /> <br /> The Pittman motor was chosen to provide enough torque to the links to overcome friction. The gear head is also needed to get the necessary torque. With the gear head, the Pittmann is capable of providing 2.1 Nm of torque, which is more than enough for this application. However, the motor is rather large and thus increases the overall weight of the system.<br /> <br /> ==Electrical Design==<br /> <br /> ==Code==<br /> <br /> ==Results and Reflections==<br /> We successfully created a climbing robot, however, the monkeybot was not as intelligent as we had originally hoped. It was unable to swing itself up from rest using a variety of closed loop control laws, most likely due to the large amounts of friction. To combat the high friction, we started the swinging link with some potential energy. From that point, it was relatively simple to design and tune an open loop time based algorithm which causes the robot to climb.<br /> <br /> A closed loop control system using encoders on both the magnets and the motor would improve this project. With this feedback, all of the necessary angles are known and thus the state of the robot is known at all times. If the robot knows its own position, it is better able to adjust to errors, such as a magnet slipping or variations in friction. An open loop time based algorithm can not adjust itself, as the timing of the sequence is hard coded.</div>

NathanHenry https://hades.mech.northwestern.edu//index.php?title=Monkeybot&diff=12630 2009-03-20T03:25:53Z

<p>NathanHenry: /* Results and Reflections */</p> <hr /> <div>[[Image:monkeybot_pic|thumb|right|350px|Moneybot Picture]]<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> ==Team Members==<br /> [[Image:Nathan_and_Nelson|thumb|right|200px|Nelson Rosa, Nathan Henry]]<br /> Nathan Henry - Senior, Mechanical Engineering&lt;br&gt;<br /> Nelson Rosa - Ph.D Student, Mechanical Engineering<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> <br /> ==Overview==<br /> The goal of this project was to create a brachiating robot capable of swinging itself side to side or climbing. This two link robot has [http://catalog.apwcompany.com/item/electromagnets/1-0-diameter-round-br-em100/em100-6-122?&amp;seo=110 electro-magnets] on each end and a DC motor at the pivot. With one magnet on, the robot swings under gravity and is aided by a input torque from the motor. This torque allows the swinging robot to overcome friction and pump energy into the system. Once the swinging arm has enough energy, the second magnet reaches a point at the same height or above the first magnet. At this point, the second magnet is turned on the motor is turned off. Now the process is repeated, swinging on the second magnet.<br /> <br /> We attempted to control the motor using both a closed loop control, with [http://www.usa.canon.com/html/industrial_encoders/lre_tr36.html rotary encoders], and an open loop control, using a time based algorithm.<br /> <br /> [http://www.youtube.com/watch?v=TA2VcH_GDJ0 Video of the monkeybot climbing]<br /> <br /> ==Geometry==<br /> [[Image:Monkeybot Geometry|thumb|left|200px|Monkeybot Geometry]]<br /> The monkeybot behaves like a double-pendulum system. The geometry, and our definitions of angles is shown to the right. The two angles important to us are the angle between the top link and a horizontal reference, and the angle between the two links. The rotary encoders over the magnet provide a measurement of the first angel, while the motor encoder measures the second.<br /> <br /> With these two angles we are able to implement a variety of control laws as described below. <br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> <br /> ==Control Method==<br /> <br /> ===Closed Loop Control===<br /> [[Image:Rotary_Encoder_TR_36|thumb|right|200px|Laser Rotary Encoder]]<br /> We first attempted to control the DC motor using feedback from a [http://www.usa.canon.com/html/industrial_encoders/lre_tr36.html rotary encoder] placed directly over each magnet. From this encoder, using both the A and B channels, we are able to determine the sign of the top link's velocity. We then implemented a simple control law in which the motor is full on in the same direction that the top link is rotating. This causes the lower link to pump in phase with the top link, mimicking the motion of a person on a swing set.<br /> <br /> With this control law we were able to pump energy into the system, however, we were never able to add enough energy to get the bottom magnet to a height equal to or above the top magnet. Starting from a resting position, with the lower link dangling straight down, the bottom link pumps in phase with the top link. The bottom magnet gradually gets higher and higher, but seems to stop increasing when it reaches a height slightly below the fixed magnet. Friction seems to be the main reason why the robot can not climb.<br /> <br /> We also implemented a control law where the lower link pumped out of phase with the top link. This caused a large increase in the movement of the top link, however, the bottom magnet stays in nearly the same position throughout.<br /> <br /> &lt;br&gt;<br /> &lt;br&gt;<br /> <br /> ===Open Loop Control===<br /> Our second approach was an open loop, time based algorithm. It involves no feedback and is just a simple set of commands implemented by the PIC. In order for the monkeybot to climb, the first link must be started with some potential energy. The magnets are both on and at the same height when the algorithm begins. The algorithm is as follows, it can be tuned by changing the values A,B,C,D which are on the order of 500-600 milliseconds.<br /> <br /> Release magnet one<br /> Motor on counterclockwise for A milliseconds<br /> Motor off<br /> Magnet one on<br /> Release magnet two<br /> Motor on counterclockwise for B milliseconds<br /> Motor off<br /> Magnet two on<br /> Release magnet two<br /> Motor on clockwise for C milliseconds<br /> Motor off<br /> Magnet two on<br /> Release magnet one<br /> Motor on clockwise for D milliseconds<br /> Motor off<br /> Magnet one on<br /> <br /> This process is repeated, and overtime, the monkeybot climbs. A video of this can be found [http://www.youtube.com/watch?v=TA2VcH_GDJ0 here.]<br /> <br /> ==Mechanical Design==<br /> ===Parts List===<br /> The robot contains:<br /> <br /> Two acrylic links<br /> Two rotational ball-bearings<br /> Two [http://catalog.apwcompany.com/item/electromagnets/1-0-diameter-round-br-em100/em100-6-122?&amp;seo=110 electro-magnets]<br /> Two [http://www.usa.canon.com/html/industrial_encoders/lre_tr36.html rotary encoders]<br /> One Pittman GM8224 DC Motor with 19.5:1 Gear Head<br /> <br /> ===Design Considerations===<br /> The two links, made of 1/8” thick acrylic, create the body of the robot and create a mount for both bearings and the motor. The thickness and the material was chosen to minimize weight, and thus the torque required to swing the robot. The links were produced using a laser cutter. The rotational ball bearings mount on the links and hold the magnets, allowing the robot to swing around a fixed point. The encoders are mounted above the magnets on a bridge, so that they are capable of measuring the rotation of the link around the magnet.<br /> <br /> The Pittman motor was chosen to provide enough torque to the links to overcome friction. The gear head is also needed to get the necessary torque. With the gear head, the Pittmann is capable of providing 2.1 Nm of torque, which is more than enough for this application. However, the motor is rather large and thus increases the overall weight of the system.<br /> <br /> ==Electrical Design==<br /> <br /> ==Code==<br /> <br /> ==Results and Reflections==<br /> We successfully created a climbing robot, however, the monkeybot was not as intelligent as we had originally hoped. It was unable to swing itself up from rest using a variety of closed loop control laws, most likely due to the large amounts of friction. To combat the high friction, we started the swinging link with some potential energy. From that point, it was relatively simple to design and tune an open loop time based algorithm which causes the robot to climb.<br /> <br /> A closed loop control system using encoders on both the magnets and the motor would improve this project. With this feedback, all of the necessary angles are known and thus the state of the robot is known at all times. If the robot knows its own position, it is better able to adjust to errors, such as a magnet slipping or variations in friction. An open loop time based algorithm can not adjust itself, as the timing of the sequence is hard coded.</div>

NathanHenry https://hades.mech.northwestern.edu//index.php?title=Monkeybot&diff=12624 2009-03-20T03:22:16Z

<p>NathanHenry: </p> <hr /> <div>[[Image:monkeybot_pic|thumb|right|350px|Moneybot Picture]]<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> ==Team Members==<br /> [[Image:Nathan_and_Nelson|thumb|right|200px|Nelson Rosa, Nathan Henry]]<br /> Nathan Henry - Senior, Mechanical Engineering&lt;br&gt;<br /> Nelson Rosa - Ph.D Student, Mechanical Engineering<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> <br /> ==Overview==<br /> The goal of this project was to create a brachiating robot capable of swinging itself side to side or climbing. This two link robot has [http://catalog.apwcompany.com/item/electromagnets/1-0-diameter-round-br-em100/em100-6-122?&amp;seo=110 electro-magnets] on each end and a DC motor at the pivot. With one magnet on, the robot swings under gravity and is aided by a input torque from the motor. This torque allows the swinging robot to overcome friction and pump energy into the system. Once the swinging arm has enough energy, the second magnet reaches a point at the same height or above the first magnet. At this point, the second magnet is turned on the motor is turned off. Now the process is repeated, swinging on the second magnet.<br /> <br /> We attempted to control the motor using both a closed loop control, with [http://www.usa.canon.com/html/industrial_encoders/lre_tr36.html rotary encoders], and an open loop control, using a time based algorithm.<br /> <br /> [http://www.youtube.com/watch?v=TA2VcH_GDJ0 Video of the monkeybot climbing]<br /> <br /> ==Geometry==<br /> [[Image:Monkeybot Geometry|thumb|left|200px|Monkeybot Geometry]]<br /> The monkeybot behaves like a double-pendulum system. The geometry, and our definitions of angles is shown to the right. The two angles important to us are the angle between the top link and a horizontal reference, and the angle between the two links. The rotary encoders over the magnet provide a measurement of the first angel, while the motor encoder measures the second.<br /> <br /> With these two angles we are able to implement a variety of control laws as described below. <br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> <br /> ==Control Method==<br /> <br /> ===Closed Loop Control===<br /> [[Image:Rotary_Encoder_TR_36|thumb|right|200px|Laser Rotary Encoder]]<br /> We first attempted to control the DC motor using feedback from a [http://www.usa.canon.com/html/industrial_encoders/lre_tr36.html rotary encoder] placed directly over each magnet. From this encoder, using both the A and B channels, we are able to determine the sign of the top link's velocity. We then implemented a simple control law in which the motor is full on in the same direction that the top link is rotating. This causes the lower link to pump in phase with the top link, mimicking the motion of a person on a swing set.<br /> <br /> With this control law we were able to pump energy into the system, however, we were never able to add enough energy to get the bottom magnet to a height equal to or above the top magnet. Starting from a resting position, with the lower link dangling straight down, the bottom link pumps in phase with the top link. The bottom magnet gradually gets higher and higher, but seems to stop increasing when it reaches a height slightly below the fixed magnet. Friction seems to be the main reason why the robot can not climb.<br /> <br /> We also implemented a control law where the lower link pumped out of phase with the top link. This caused a large increase in the movement of the top link, however, the bottom magnet stays in nearly the same position throughout.<br /> <br /> &lt;br&gt;<br /> &lt;br&gt;<br /> <br /> ===Open Loop Control===<br /> Our second approach was an open loop, time based algorithm. It involves no feedback and is just a simple set of commands implemented by the PIC. In order for the monkeybot to climb, the first link must be started with some potential energy. The magnets are both on and at the same height when the algorithm begins. The algorithm is as follows, it can be tuned by changing the values A,B,C,D which are on the order of 500-600 milliseconds.<br /> <br /> Release magnet one<br /> Motor on counterclockwise for A milliseconds<br /> Motor off<br /> Magnet one on<br /> Release magnet two<br /> Motor on counterclockwise for B milliseconds<br /> Motor off<br /> Magnet two on<br /> Release magnet two<br /> Motor on clockwise for C milliseconds<br /> Motor off<br /> Magnet two on<br /> Release magnet one<br /> Motor on clockwise for D milliseconds<br /> Motor off<br /> Magnet one on<br /> <br /> This process is repeated, and overtime, the monkeybot climbs. A video of this can be found [http://www.youtube.com/watch?v=TA2VcH_GDJ0 here.]<br /> <br /> ==Mechanical Design==<br /> ===Parts List===<br /> The robot contains:<br /> <br /> Two acrylic links<br /> Two rotational ball-bearings<br /> Two [http://catalog.apwcompany.com/item/electromagnets/1-0-diameter-round-br-em100/em100-6-122?&amp;seo=110 electro-magnets]<br /> Two [http://www.usa.canon.com/html/industrial_encoders/lre_tr36.html rotary encoders]<br /> One Pittman GM8224 DC Motor with 19.5:1 Gear Head<br /> <br /> ===Design Considerations===<br /> The two links, made of 1/8” thick acrylic, create the body of the robot and create a mount for both bearings and the motor. The thickness and the material was chosen to minimize weight, and thus the torque required to swing the robot. The links were produced using a laser cutter. The rotational ball bearings mount on the links and hold the magnets, allowing the robot to swing around a fixed point. The encoders are mounted above the magnets on a bridge, so that they are capable of measuring the rotation of the link around the magnet.<br /> <br /> The Pittman motor was chosen to provide enough torque to the links to overcome friction. The gear head is also needed to get the necessary torque. With the gear head, the Pittmann is capable of providing 2.1 Nm of torque, which is more than enough for this application. However, the motor is rather large and thus increases the overall weight of the system.<br /> <br /> ==Electrical Design==<br /> <br /> ==Code==<br /> <br /> ==Results and Reflections==<br /> We successfully created a climbing robot, however, the monkeybot was not as intelligent as we had originally hoped. It was unable to swing itself up from rest using a variety of closed loop control laws, most likely due to the large amounts of friction. To combat the high friction, we started the swinging link with some potential energy. From that point, it was relatively simple to design and tune an open loop time based algorithm which causes the robot to climb.</div>

NathanHenry https://hades.mech.northwestern.edu//index.php?title=Monkeybot&diff=12612 2009-03-20T03:16:48Z

<p>NathanHenry: </p> <hr /> <div>[[Image:monkeybot_pic|thumb|right|350px|Moneybot Picture]]<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> ==Team Members==<br /> [[Image:Nathan_and_Nelson|thumb|right|200px|Nelson Rosa, Nathan Henry]]<br /> Nathan Henry - Senior, Mechanical Engineering&lt;br&gt;<br /> Nelson Rosa - Ph.D Student, Mechanical Engineering<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> <br /> ==Overview==<br /> The goal of this project was to create a brachiating robot capable of swinging itself side to side or climbing. This two link robot has [http://catalog.apwcompany.com/item/electromagnets/1-0-diameter-round-br-em100/em100-6-122?&amp;seo=110 electro-magnets] on each end and a DC motor at the pivot. With one magnet on, the robot swings under gravity and is aided by a input torque from the motor. This torque allows the swinging robot to overcome friction and pump energy into the system. Once the swinging arm has enough energy, the second magnet reaches a point at the same height or above the first magnet. At this point, the second magnet is turned on the motor is turned off. Now the process is repeated, swinging on the second magnet.<br /> <br /> We attempted to control the motor using both a closed loop control, with [http://www.usa.canon.com/html/industrial_encoders/lre_tr36.html rotary encoders], and an open loop control, using a time based algorithm.<br /> <br /> [http://www.youtube.com/watch?v=TA2VcH_GDJ0 Video of the monkeybot climbing]<br /> <br /> ==Geometry==<br /> [[Image:Monkeybot Geometry|thumb|left|200px|Monkeybot Geometry]]<br /> The monkeybot behaves like a double-pendulum system. The geometry, and our definitions of angles is shown to the right. The two angles important to us are the angle between the top link and a horizontal reference, and the angle between the two links. The rotary encoders over the magnet provide a measurement of the first angel, while the motor encoder measures the second.<br /> <br /> With these two angles we are able to implement a variety of control laws as described below. <br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> <br /> ==Control Method==<br /> <br /> ===Closed Loop Control===<br /> [[Image:Rotary_Encoder_TR_36|thumb|right|200px|Laser Rotary Encoder]]<br /> We first attempted to control the DC motor using feedback from a [http://www.usa.canon.com/html/industrial_encoders/lre_tr36.html rotary encoder] placed directly over each magnet. From this encoder, using both the A and B channels, we are able to determine the sign of the top link's velocity. We then implemented a simple control law in which the motor is full on in the same direction that the top link is rotating. This causes the lower link to pump in phase with the top link, mimicking the motion of a person on a swing set.<br /> <br /> With this control law we were able to pump energy into the system, however, we were never able to add enough energy to get the bottom magnet to a height equal to or above the top magnet. Starting from a resting position, with the lower link dangling straight down, the bottom link pumps in phase with the top link. The bottom magnet gradually gets higher and higher, but seems to stop increasing when it reaches a height slightly below the fixed magnet. Friction seems to be the main reason why the robot can not climb.<br /> <br /> We also implemented a control law where the lower link pumped out of phase with the top link. This caused a large increase in the movement of the top link, however, the bottom magnet stays in nearly the same position throughout.<br /> <br /> &lt;br&gt;<br /> &lt;br&gt;<br /> <br /> ===Open Loop Control===<br /> Our second approach was an open loop, time based algorithm. It involves no feedback and is just a simple set of commands implemented by the PIC. In order for the monkeybot to climb, the first link must be started with some potential energy. The magnets are both on and at the same height when the algorithm begins. The algorithm is as follows, it can be tuned by changing the values A,B,C,D which are on the order of 500-600 milliseconds.<br /> <br /> Release magnet one<br /> Motor on counterclockwise for A milliseconds<br /> Motor off<br /> Magnet one on<br /> Release magnet two<br /> Motor on counterclockwise for B milliseconds<br /> Motor off<br /> Magnet two on<br /> Release magnet two<br /> Motor on clockwise for C milliseconds<br /> Motor off<br /> Magnet two on<br /> Release magnet one<br /> Motor on clockwise for D milliseconds<br /> Motor off<br /> Magnet one on<br /> <br /> This process is repeated, and overtime, the monkeybot climbs. A video of this can be found [http://www.youtube.com/watch?v=TA2VcH_GDJ0 here.]<br /> <br /> ==Mechanical Design==<br /> ===Parts List===<br /> The robot contains:<br /> <br /> Two acrylic links<br /> Two rotational ball-bearings<br /> Two [http://catalog.apwcompany.com/item/electromagnets/1-0-diameter-round-br-em100/em100-6-122?&amp;seo=110 electro-magnets]<br /> Two [http://www.usa.canon.com/html/industrial_encoders/lre_tr36.html rotary encoders]<br /> One Pittman GM8224 DC Motor with 19.5:1 Gear Head<br /> <br /> ===Design Considerations===<br /> The two links, made of 1/8” thick acrylic, create the body of the robot and create a mount for both bearings and the motor. THe thickness and the material was chosen to minimize weight, and thus the torque required to swing the robot. The links were produced using a laser cutter. The rotational ball bearings mount on the links and hold the magnets, allowing the robot to swing around a fixed point. The encoders are mounted above the magnets on a bridge, so that they are capable of measuring the rotation of the link around the magnet.<br /> <br /> The Pittman motor was chosen to provide enough torque to the links to overcome friction. The gear head is also needed to get the necessary torque. With the gear head, the Pittmann is capable of providing 2.1 Nm of torque, which is more than enough for this application. However, the motor is rather large and thus increases the overall weight of the system.<br /> <br /> ==Electrical Design==<br /> <br /> ==Code==<br /> <br /> ==Results and Reflections==</div>

NathanHenry https://hades.mech.northwestern.edu//index.php?title=Monkeybot&diff=12611 2009-03-20T03:16:30Z

<p>NathanHenry: </p> <hr /> <div>[[Image:monkeybot_pic|thumb|right|350px|Moneybot Picture]]<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> ==Team Members==<br /> [[Image:Nathan_and_Nelson|thumb|right|200px|Nelson Rosa, Nathan Henry]]<br /> Nathan Henry - Senior, Mechanical Engineering&lt;br&gt;<br /> Nelson Rosa - Ph.D Student, Mechanical Engineering<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> <br /> ==Overview==<br /> The goal of this project was to create a brachiating robot capable of swinging itself side to side or climbing. This two link robot has [http://catalog.apwcompany.com/item/electromagnets/1-0-diameter-round-br-em100/em100-6-122?&amp;seo=110 electro-magnets] on each end and a DC motor at the pivot. With one magnet on, the robot swings under gravity and is aided by a input torque from the motor. This torque allows the swinging robot to overcome friction and pump energy into the system. Once the swinging arm has enough energy, the second magnet reaches a point at the same height or above the first magnet. At this point, the second magnet is turned on the motor is turned off. Now the process is repeated, swinging on the second magnet.<br /> <br /> We attempted to control the motor using both a closed loop control, with [http://www.usa.canon.com/html/industrial_encoders/lre_tr36.html rotary encoders], and an open loop control, using a time based algorithm.<br /> <br /> [http://www.youtube.com/watch?v=TA2VcH_GDJ0 Video of the monkeybot climbing]<br /> <br /> ==Geometry==<br /> [[Image:Monkeybot Geometry|thumb|left|200px|Monkeybot Geometry]]<br /> The monkeybot behaves like a double-pendulum system. The geometry, and our definitions of angles is shown to the right. The two angles important to us are the angle between the top link and a horizontal reference, and the angle between the two links. The rotary encoders over the magnet provide a measurement of the first angel, while the motor encoder measures the second.<br /> <br /> With these two angles we are able to implement a variety of control laws as described below. <br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> <br /> ==Control Method==<br /> <br /> ===Closed Loop Control===<br /> [[Image:Rotary_Encoder_TR_36|thumb|right|200px|Laser Rotary Encoder]]<br /> We first attempted to control the DC motor using feedback from a [http://www.usa.canon.com/html/industrial_encoders/lre_tr36.html rotary encoder] placed directly over each magnet. From this encoder, using both the A and B channels, we are able to determine the sign of the top link's velocity. We then implemented a simple control law in which the motor is full on in the same direction that the top link is rotating. This causes the lower link to pump in phase with the top link, mimicking the motion of a person on a swing set.<br /> <br /> With this control law we were able to pump energy into the system, however, we were never able to add enough energy to get the bottom magnet to a height equal to or above the top magnet. Starting from a resting position, with the lower link dangling straight down, the bottom link pumps in phase with the top link. The bottom magnet gradually gets higher and higher, but seems to stop increasing when it reaches a height slightly below the fixed magnet. Friction seems to be the main reason why the robot can not climb.<br /> <br /> We also implemented a control law where the lower link pumped out of phase with the top link. This caused a large increase in the movement of the top link, however, the bottom magnet stays in nearly the same position throughout.<br /> <br /> &lt;br&gt;<br /> &lt;br&gt;<br /> <br /> ===Open Loop Control===<br /> Our second approach was an open loop, time based algorithm. It involves no feedback and is just a simple set of commands implemented by the PIC. In order for the monkeybot to climb, the first link must be started with some potential energy. The magnets are both on and at the same height when the algorithm begins. The algorithm is as follows, it can be tuned by changing the values A,B,C,D which are on the order of 500-600 milliseconds.<br /> <br /> Release magnet one<br /> Motor on counterclockwise for A milliseconds<br /> Motor off<br /> Magnet one on<br /> Release magnet two<br /> Motor on counterclockwise for B milliseconds<br /> Motor off<br /> Magnet two on<br /> Release magnet two<br /> Motor on clockwise for C milliseconds<br /> Motor off<br /> Magnet two on<br /> Release magnet one<br /> Motor on clockwise for D milliseconds<br /> Motor off<br /> Magnet one on<br /> <br /> This process is repeated, and overtime, the monkeybot climbs. A video of this can be found [http://www.youtube.com/watch?v=TA2VcH_GDJ0 here.]<br /> <br /> ==Mechanical Design==<br /> ===Parts List===<br /> The robot contains:<br /> <br /> Two acrylic links<br /> Two rotational ball-bearings<br /> Two [http://catalog.apwcompany.com/item/electromagnets/1-0-diameter-round-br-em100/em100-6-122?&amp;seo=110 electro-magnets]<br /> Two [http://www.usa.canon.com/html/industrial_encoders/lre_tr36.html rotary encoders]<br /> One Pittman GM8224 DC Motor with 19.5:1 Gear Head<br /> <br /> ===Design Considerations===<br /> The two links, made of 1/8” thick acrylic, create the body of the robot and create a mount for both bearings and the motor. THe thickness and the material was chosen to minimize weight, and thus the torque required to swing the robot. The links were produced using a laser cutter. The rotational ball bearings mount on the links and hold the magnets, allowing the robot to swing around a fixed point. The encoders are mounted above the magnets on a bridge, so that they are capable of measuring the rotation of the link around the magnet.<br /> <br /> The Pittman motor was chosen to provide enough torque to the links to overcome friction. The gear head is also needed to get the necessary torque. With the gear head, the Pittmann is capable of providing 2.1 Nm of torque, which is more than enough for this application. However, the motor is rather large and thus increases the overall weight of the system.<br /> <br /> ==Electrical Design==<br /> <br /> ==Code==<br /> <br /> ==Results and Reflections==</div>

NathanHenry https://hades.mech.northwestern.edu//index.php?title=Monkeybot&diff=12610 2009-03-20T03:16:10Z

<p>NathanHenry: </p> <hr /> <div>[[Image:monkeybot_pic|thumb|right|350px|Moneybot Picture]]<br /> ==Team Members==<br /> [[Image:Nathan_and_Nelson|thumb|right|200px|Nelson Rosa, Nathan Henry]]<br /> Nathan Henry - Senior, Mechanical Engineering&lt;br&gt;<br /> Nelson Rosa - Ph.D Student, Mechanical Engineering<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> <br /> ==Overview==<br /> The goal of this project was to create a brachiating robot capable of swinging itself side to side or climbing. This two link robot has [http://catalog.apwcompany.com/item/electromagnets/1-0-diameter-round-br-em100/em100-6-122?&amp;seo=110 electro-magnets] on each end and a DC motor at the pivot. With one magnet on, the robot swings under gravity and is aided by a input torque from the motor. This torque allows the swinging robot to overcome friction and pump energy into the system. Once the swinging arm has enough energy, the second magnet reaches a point at the same height or above the first magnet. At this point, the second magnet is turned on the motor is turned off. Now the process is repeated, swinging on the second magnet.<br /> <br /> We attempted to control the motor using both a closed loop control, with [http://www.usa.canon.com/html/industrial_encoders/lre_tr36.html rotary encoders], and an open loop control, using a time based algorithm.<br /> <br /> [http://www.youtube.com/watch?v=TA2VcH_GDJ0 Video of the monkeybot climbing]<br /> <br /> ==Geometry==<br /> [[Image:Monkeybot Geometry|thumb|left|200px|Monkeybot Geometry]]<br /> The monkeybot behaves like a double-pendulum system. The geometry, and our definitions of angles is shown to the right. The two angles important to us are the angle between the top link and a horizontal reference, and the angle between the two links. The rotary encoders over the magnet provide a measurement of the first angel, while the motor encoder measures the second.<br /> <br /> With these two angles we are able to implement a variety of control laws as described below. <br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> <br /> ==Control Method==<br /> <br /> ===Closed Loop Control===<br /> [[Image:Rotary_Encoder_TR_36|thumb|right|200px|Laser Rotary Encoder]]<br /> We first attempted to control the DC motor using feedback from a [http://www.usa.canon.com/html/industrial_encoders/lre_tr36.html rotary encoder] placed directly over each magnet. From this encoder, using both the A and B channels, we are able to determine the sign of the top link's velocity. We then implemented a simple control law in which the motor is full on in the same direction that the top link is rotating. This causes the lower link to pump in phase with the top link, mimicking the motion of a person on a swing set.<br /> <br /> With this control law we were able to pump energy into the system, however, we were never able to add enough energy to get the bottom magnet to a height equal to or above the top magnet. Starting from a resting position, with the lower link dangling straight down, the bottom link pumps in phase with the top link. The bottom magnet gradually gets higher and higher, but seems to stop increasing when it reaches a height slightly below the fixed magnet. Friction seems to be the main reason why the robot can not climb.<br /> <br /> We also implemented a control law where the lower link pumped out of phase with the top link. This caused a large increase in the movement of the top link, however, the bottom magnet stays in nearly the same position throughout.<br /> <br /> &lt;br&gt;<br /> &lt;br&gt;<br /> <br /> ===Open Loop Control===<br /> Our second approach was an open loop, time based algorithm. It involves no feedback and is just a simple set of commands implemented by the PIC. In order for the monkeybot to climb, the first link must be started with some potential energy. The magnets are both on and at the same height when the algorithm begins. The algorithm is as follows, it can be tuned by changing the values A,B,C,D which are on the order of 500-600 milliseconds.<br /> <br /> Release magnet one<br /> Motor on counterclockwise for A milliseconds<br /> Motor off<br /> Magnet one on<br /> Release magnet two<br /> Motor on counterclockwise for B milliseconds<br /> Motor off<br /> Magnet two on<br /> Release magnet two<br /> Motor on clockwise for C milliseconds<br /> Motor off<br /> Magnet two on<br /> Release magnet one<br /> Motor on clockwise for D milliseconds<br /> Motor off<br /> Magnet one on<br /> <br /> This process is repeated, and overtime, the monkeybot climbs. A video of this can be found [http://www.youtube.com/watch?v=TA2VcH_GDJ0 here.]<br /> <br /> ==Mechanical Design==<br /> ===Parts List===<br /> The robot contains:<br /> <br /> Two acrylic links<br /> Two rotational ball-bearings<br /> Two [http://catalog.apwcompany.com/item/electromagnets/1-0-diameter-round-br-em100/em100-6-122?&amp;seo=110 electro-magnets]<br /> Two [http://www.usa.canon.com/html/industrial_encoders/lre_tr36.html rotary encoders]<br /> One Pittman GM8224 DC Motor with 19.5:1 Gear Head<br /> <br /> ===Design Considerations===<br /> The two links, made of 1/8” thick acrylic, create the body of the robot and create a mount for both bearings and the motor. THe thickness and the material was chosen to minimize weight, and thus the torque required to swing the robot. The links were produced using a laser cutter. The rotational ball bearings mount on the links and hold the magnets, allowing the robot to swing around a fixed point. The encoders are mounted above the magnets on a bridge, so that they are capable of measuring the rotation of the link around the magnet.<br /> <br /> The Pittman motor was chosen to provide enough torque to the links to overcome friction. The gear head is also needed to get the necessary torque. With the gear head, the Pittmann is capable of providing 2.1 Nm of torque, which is more than enough for this application. However, the motor is rather large and thus increases the overall weight of the system.<br /> <br /> ==Electrical Design==<br /> <br /> ==Code==<br /> <br /> ==Results and Reflections==</div>

NathanHenry https://hades.mech.northwestern.edu//index.php?title=File:Monkeybot_pic&diff=12606 2009-03-20T03:15:20Z

<p>NathanHenry: monkeybot picture</p> <hr /> <div>monkeybot picture</div>

NathanHenry https://hades.mech.northwestern.edu//index.php?title=Monkeybot&diff=12604 2009-03-20T03:13:49Z

<p>NathanHenry: </p> <hr /> <div>[[Image:monkeybot_pic|thumb|right|400px|Moneybot Picture]]<br /> ==Team Members==<br /> [[Image:Nathan_and_Nelson|thumb|right|200px|Nelson Rosa, Nathan Henry]]<br /> Nathan Henry - Senior, Mechanical Engineering&lt;br&gt;<br /> Nelson Rosa - Ph.D Student, Mechanical Engineering<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> <br /> ==Overview==<br /> The goal of this project was to create a brachiating robot capable of swinging itself side to side or climbing. This two link robot has [http://catalog.apwcompany.com/item/electromagnets/1-0-diameter-round-br-em100/em100-6-122?&amp;seo=110 electro-magnets] on each end and a DC motor at the pivot. With one magnet on, the robot swings under gravity and is aided by a input torque from the motor. This torque allows the swinging robot to overcome friction and pump energy into the system. Once the swinging arm has enough energy, the second magnet reaches a point at the same height or above the first magnet. At this point, the second magnet is turned on the motor is turned off. Now the process is repeated, swinging on the second magnet.<br /> <br /> We attempted to control the motor using both a closed loop control, with [http://www.usa.canon.com/html/industrial_encoders/lre_tr36.html rotary encoders], and an open loop control, using a time based algorithm.<br /> <br /> [http://www.youtube.com/watch?v=TA2VcH_GDJ0 Video of the monkeybot climbing]<br /> <br /> ==Geometry==<br /> [[Image:Monkeybot Geometry|thumb|left|200px|Monkeybot Geometry]]<br /> The monkeybot behaves like a double-pendulum system. The geometry, and our definitions of angles is shown to the right. The two angles important to us are the angle between the top link and a horizontal reference, and the angle between the two links. The rotary encoders over the magnet provide a measurement of the first angel, while the motor encoder measures the second.<br /> <br /> With these two angles we are able to implement a variety of control laws as described below. <br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> <br /> ==Control Method==<br /> <br /> ===Closed Loop Control===<br /> [[Image:Rotary_Encoder_TR_36|thumb|right|200px|Laser Rotary Encoder]]<br /> We first attempted to control the DC motor using feedback from a [http://www.usa.canon.com/html/industrial_encoders/lre_tr36.html rotary encoder] placed directly over each magnet. From this encoder, using both the A and B channels, we are able to determine the sign of the top link's velocity. We then implemented a simple control law in which the motor is full on in the same direction that the top link is rotating. This causes the lower link to pump in phase with the top link, mimicking the motion of a person on a swing set.<br /> <br /> With this control law we were able to pump energy into the system, however, we were never able to add enough energy to get the bottom magnet to a height equal to or above the top magnet. Starting from a resting position, with the lower link dangling straight down, the bottom link pumps in phase with the top link. The bottom magnet gradually gets higher and higher, but seems to stop increasing when it reaches a height slightly below the fixed magnet. Friction seems to be the main reason why the robot can not climb.<br /> <br /> We also implemented a control law where the lower link pumped out of phase with the top link. This caused a large increase in the movement of the top link, however, the bottom magnet stays in nearly the same position throughout.<br /> <br /> &lt;br&gt;<br /> &lt;br&gt;<br /> <br /> ===Open Loop Control===<br /> Our second approach was an open loop, time based algorithm. It involves no feedback and is just a simple set of commands implemented by the PIC. In order for the monkeybot to climb, the first link must be started with some potential energy. The magnets are both on and at the same height when the algorithm begins. The algorithm is as follows, it can be tuned by changing the values A,B,C,D which are on the order of 500-600 milliseconds.<br /> <br /> Release magnet one<br /> Motor on counterclockwise for A milliseconds<br /> Motor off<br /> Magnet one on<br /> Release magnet two<br /> Motor on counterclockwise for B milliseconds<br /> Motor off<br /> Magnet two on<br /> Release magnet two<br /> Motor on clockwise for C milliseconds<br /> Motor off<br /> Magnet two on<br /> Release magnet one<br /> Motor on clockwise for D milliseconds<br /> Motor off<br /> Magnet one on<br /> <br /> This process is repeated, and overtime, the monkeybot climbs. A video of this can be found [http://www.youtube.com/watch?v=TA2VcH_GDJ0 here.]<br /> <br /> ==Mechanical Design==<br /> ===Parts List===<br /> The robot contains:<br /> <br /> Two acrylic links<br /> Two rotational ball-bearings<br /> Two [http://catalog.apwcompany.com/item/electromagnets/1-0-diameter-round-br-em100/em100-6-122?&amp;seo=110 electro-magnets]<br /> Two [http://www.usa.canon.com/html/industrial_encoders/lre_tr36.html rotary encoders]<br /> One Pittman GM8224 DC Motor with 19.5:1 Gear Head<br /> <br /> ===Design Considerations===<br /> The two links, made of 1/8” thick acrylic, create the body of the robot and create a mount for both bearings and the motor. THe thickness and the material was chosen to minimize weight, and thus the torque required to swing the robot. The links were produced using a laser cutter. The rotational ball bearings mount on the links and hold the magnets, allowing the robot to swing around a fixed point. The encoders are mounted above the magnets on a bridge, so that they are capable of measuring the rotation of the link around the magnet.<br /> <br /> The Pittman motor was chosen to provide enough torque to the links to overcome friction. The gear head is also needed to get the necessary torque. With the gear head, the Pittmann is capable of providing 2.1 Nm of torque, which is more than enough for this application. However, the motor is rather large and thus increases the overall weight of the system.<br /> <br /> ==Electrical Design==<br /> <br /> ==Code==<br /> <br /> ==Results and Reflections==</div>

NathanHenry https://hades.mech.northwestern.edu//index.php?title=Monkeybot&diff=11362 2009-03-18T03:31:32Z

<p>NathanHenry: </p> <hr /> <div>==Team Members==<br /> [[Image:Nathan_and_Nelson|thumb|right|200px|Nelson Rosa, Nathan Henry]]<br /> Nathan Henry - Senior, Mechanical Engineering&lt;br&gt;<br /> Nelson Rosa - Ph.D Student, Mechanical Engineering<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> <br /> ==Overview==<br /> The goal of this project was to create a brachiating robot capable of swinging itself side to side or climbing. This two link robot has [http://catalog.apwcompany.com/item/electromagnets/1-0-diameter-round-br-em100/em100-6-122?&amp;seo=110 electro-magnets] on each end and a DC motor at the pivot. With one magnet on, the robot swings under gravity and is aided by a input torque from the motor. This torque allows the swinging robot to overcome friction and pump energy into the system. Once the swinging arm has enough energy, the second magnet reaches a point at the same height or above the first magnet. At this point, the second magnet is turned on the motor is turned off. Now the process is repeated, swinging on the second magnet.<br /> <br /> We attempted to control the motor using both a closed loop control, with [http://www.usa.canon.com/html/industrial_encoders/lre_tr36.html rotary encoders], and an open loop control, using a time based algorithm.<br /> <br /> [http://www.youtube.com/watch?v=TA2VcH_GDJ0 Video of the monkeybot climbing]<br /> <br /> ==Geometry==<br /> [[Image:Monkeybot Geometry|thumb|left|200px|Monkeybot Geometry]]<br /> The monkeybot behaves like a double-pendulum system. The geometry, and our definitions of angles is shown to the right. The two angles important to us are the angle between the top link and a horizontal reference, and the angle between the two links. The rotary encoders over the magnet provide a measurement of the first angel, while the motor encoder measures the second.<br /> <br /> With these two angles we are able to implement a variety of control laws as described below. <br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> <br /> ==Control Method==<br /> <br /> ===Closed Loop Control===<br /> [[Image:Rotary_Encoder_TR_36|thumb|right|200px|Laser Rotary Encoder]]<br /> We first attempted to control the DC motor using feedback from a [http://www.usa.canon.com/html/industrial_encoders/lre_tr36.html rotary encoder] placed directly over each magnet. From this encoder, using both the A and B channels, we are able to determine the sign of the top link's velocity. We then implemented a simple control law in which the motor is full on in the same direction that the top link is rotating. This causes the lower link to pump in phase with the top link, mimicking the motion of a person on a swing set.<br /> <br /> With this control law we were able to pump energy into the system, however, we were never able to add enough energy to get the bottom magnet to a height equal to or above the top magnet. Starting from a resting position, with the lower link dangling straight down, the bottom link pumps in phase with the top link. The bottom magnet gradually gets higher and higher, but seems to stop increasing when it reaches a height slightly below the fixed magnet. Friction seems to be the main reason why the robot can not climb.<br /> <br /> We also implemented a control law where the lower link pumped out of phase with the top link. This caused a large increase in the movement of the top link, however, the bottom magnet stays in nearly the same position throughout.<br /> <br /> &lt;br&gt;<br /> &lt;br&gt;<br /> <br /> ===Open Loop Control===<br /> Our second approach was an open loop, time based algorithm. It involves no feedback and is just a simple set of commands implemented by the PIC. In order for the monkeybot to climb, the first link must be started with some potential energy. The magnets are both on and at the same height when the algorithm begins. The algorithm is as follows, it can be tuned by changing the values A,B,C,D which are on the order of 500-600 milliseconds.<br /> <br /> Release magnet one<br /> Motor on counterclockwise for A milliseconds<br /> Motor off<br /> Magnet one on<br /> Release magnet two<br /> Motor on counterclockwise for B milliseconds<br /> Motor off<br /> Magnet two on<br /> Release magnet two<br /> Motor on clockwise for C milliseconds<br /> Motor off<br /> Magnet two on<br /> Release magnet one<br /> Motor on clockwise for D milliseconds<br /> Motor off<br /> Magnet one on<br /> <br /> This process is repeated, and overtime, the monkeybot climbs. A video of this can be found [http://www.youtube.com/watch?v=TA2VcH_GDJ0 here.]<br /> <br /> ==Mechanical Design==<br /> ===Parts List===<br /> The robot contains:<br /> <br /> Two acrylic links<br /> Two rotational ball-bearings<br /> Two [http://catalog.apwcompany.com/item/electromagnets/1-0-diameter-round-br-em100/em100-6-122?&amp;seo=110 electro-magnets]<br /> Two [http://www.usa.canon.com/html/industrial_encoders/lre_tr36.html rotary encoders]<br /> One Pittman GM8224 DC Motor with 19.5:1 Gear Head<br /> <br /> ===Design Considerations===<br /> The two links, made of 1/8” thick acrylic, create the body of the robot and create a mount for both bearings and the motor. THe thickness and the material was chosen to minimize weight, and thus the torque required to swing the robot. The links were produced using a laser cutter. The rotational ball bearings mount on the links and hold the magnets, allowing the robot to swing around a fixed point. The encoders are mounted above the magnets on a bridge, so that they are capable of measuring the rotation of the link around the magnet.<br /> <br /> The Pittman motor was chosen to provide enough torque to the links to overcome friction. The gear head is also needed to get the necessary torque. With the gear head, the Pittmann is capable of providing 2.1 Nm of torque, which is more than enough for this application. However, the motor is rather large and thus increases the overall weight of the system.<br /> <br /> ==Electrical Design==<br /> <br /> ==Code==<br /> <br /> ==Results and Reflections==</div>

NathanHenry https://hades.mech.northwestern.edu//index.php?title=Monkeybot&diff=11361 2009-03-18T03:26:22Z

<p>NathanHenry: </p> <hr /> <div>==Team Members==<br /> [[Image:Nathan_and_Nelson|thumb|right|200px|Nelson Rosa, Nathan Henry]]<br /> Nathan Henry - Senior, Mechanical Engineering&lt;br&gt;<br /> Nelson Rosa - Ph.D Student, Mechanical Engineering<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> <br /> ==Overview==<br /> The goal of this project was to create a brachiating robot capable of swinging itself side to side or climbing. This two link robot has [http://catalog.apwcompany.com/item/electromagnets/1-0-diameter-round-br-em100/em100-6-122?&amp;seo=110 electro-magnets] on each end and a DC motor at the pivot. With one magnet on, the robot swings under gravity and is aided by a input torque from the motor. This torque allows the swinging robot to overcome friction and pump energy into the system. Once the swinging arm has enough energy, the second magnet reaches a point at the same height or above the first magnet. At this point, the second magnet is turned on the motor is turned off. Now the process is repeated, swinging on the second magnet.<br /> <br /> We attempted to control the motor using both a closed loop control, with [http://www.usa.canon.com/html/industrial_encoders/lre_tr36.html rotary encoders], and an open loop control, using a time based algorithm.<br /> <br /> [http://www.youtube.com/watch?v=TA2VcH_GDJ0 Video of the monkeybot climbing]<br /> <br /> ==Geometry==<br /> [[Image:Monkeybot Geometry|thumb|left|200px|Monkeybot Geometry]]<br /> The monkeybot behaves like a double-pendulum system. The geometry, and our definitions of angles is shown to the right. The two angles important to us are the angle between the top link and a horizontal reference, and the angle between the two links. The rotary encoders over the magnet provide a measurement of the first angel, while the motor encoder measures the second.<br /> <br /> With these two angles we are able to implement a variety of control laws as described below. <br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> <br /> ==Control Method==<br /> <br /> ===Closed Loop Control===<br /> [[Image:Rotary_Encoder_TR_36|thumb|right|200px|Laser Rotary Encoder]]<br /> We first attempted to control the DC motor using feedback from a [http://www.usa.canon.com/html/industrial_encoders/lre_tr36.html rotary encoder] placed directly over each magnet. From this encoder, using both the A and B channels, we are able to determine the sign of the top link's velocity. We then implemented a simple control law in which the motor is full on in the same direction that the top link is rotating. This causes the lower link to pump in phase with the top link, mimicking the motion of a person on a swing set.<br /> <br /> With this control law we were able to pump energy into the system, however, we were never able to add enough energy to get the bottom magnet to a height equal to or above the top magnet. Starting from a resting position, with the lower link dangling straight down, the bottom link pumps in phase with the top link. The bottom magnet gradually gets higher and higher, but seems to stop increasing when it reaches a height slightly below the fixed magnet. Friction seems to be the main reason why the robot can not climb.<br /> <br /> We also implemented a control law where the lower link pumped out of phase with the top link. This caused a large increase in the movement of the top link, however, the bottom magnet stays in nearly the same position throughout.<br /> <br /> &lt;br&gt;<br /> &lt;br&gt;<br /> <br /> ===Open Loop Control===<br /> Our second approach was an open loop, time based algorithm. It involves no feedback and is just a simple set of commands implemented by the PIC. In order for the monkeybot to climb, the first link must be started with some potential energy. The magnets are both on and at the same height when the algorithm begins. The algorithm is as follows, it can be tuned by changing the values A,B,C,D which are on the order of 500-600 milliseconds.<br /> <br /> Release magnet one<br /> Motor on counterclockwise for A milliseconds<br /> Motor off<br /> Magnet one on<br /> Release magnet two<br /> Motor on counterclockwise for B milliseconds<br /> Motor off<br /> Magnet two on<br /> Release magnet two<br /> Motor on clockwise for C milliseconds<br /> Motor off<br /> Magnet two on<br /> Release magnet one<br /> Motor on clockwise for D milliseconds<br /> Motor off<br /> Magnet one on<br /> <br /> This process is repeated, and overtime, the monkeybot climbs. A video of this can be found [http://www.youtube.com/watch?v=TA2VcH_GDJ0 here.]<br /> <br /> ==Mechanical Design==<br /> ===Parts List===<br /> The robot contains:<br /> <br /> Two acrylic links<br /> Two rotational ball-bearings<br /> Two [http://catalog.apwcompany.com/item/electromagnets/1-0-diameter-round-br-em100/em100-6-122?&amp;seo=110 electro-magnets]<br /> Two [http://www.usa.canon.com/html/industrial_encoders/lre_tr36.html rotary encoders]<br /> One Pittman GM8224 DC Motor with 19.5:1 Gear Head<br /> <br /> The two links, made of 1/8” thick acrylic, create the body of the robot and create a mount for both bearings and the motor. The links were produced using a laser cutter. The rotational ball bearings mount on the links and hold the magnets, allowing the robot to swing around a fixed point. The encoders are mounted above the magnets on a bridge, so that they are capable of measuring the rotation of the link around the magnet.<br /> <br /> The Pittman motor was chosen to provide enough torque to the links to overcome friction. The gear head is also needed to get the necessary torque.<br /> <br /> ==Electrical Design==<br /> <br /> ==Code==<br /> <br /> ==Results and Reflections==</div>

NathanHenry https://hades.mech.northwestern.edu//index.php?title=Monkeybot&diff=11360 2009-03-18T03:24:55Z

<p>NathanHenry: /* Mechanical Design */</p> <hr /> <div>==Team Members==<br /> [[Image:Nathan_and_Nelson|thumb|right|200px|Nelson Rosa, Nathan Henry]]<br /> Nathan Henry - Senior, Mechanical Engineering&lt;br&gt;<br /> Nelson Rosa - Ph.D Student, Mechanical Engineering<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> <br /> ==Overview==<br /> The goal of this project was to create a brachiating robot capable of swinging itself side to side or climbing. This two link robot has [http://catalog.apwcompany.com/item/electromagnets/1-0-diameter-round-br-em100/em100-6-122?&amp;seo=110 electro-magnets] on each end and a DC motor at the pivot. With one magnet on, the robot swings under gravity and is aided by a input torque from the motor. This torque allows the swinging robot to overcome friction and pump energy into the system. Once the swinging arm has enough energy, the second magnet reaches a point at the same height or above the first magnet. At this point, the second magnet is turned on the motor is turned off. Now the process is repeated, swinging on the second magnet.<br /> <br /> We attempted to control the motor using both a closed loop control, with [http://www.usa.canon.com/html/industrial_encoders/lre_tr36.html rotary encoders], and an open loop control, using a time based algorithm.<br /> <br /> [http://www.youtube.com/watch?v=TA2VcH_GDJ0 Video of the monkeybot climbing]<br /> <br /> ==Geometry==<br /> [[Image:Monkeybot Geometry|thumb|left|200px|Monkeybot Geometry]]<br /> The monkeybot behaves like a double-pendulum system. The geometry, and our definitions of angles is shown to the right. The two angles important to us are the angle between the top link and a horizontal reference, and the angle between the two links. The rotary encoders over the magnet provide a measurement of the first angel, while the motor encoder measures the second.<br /> <br /> With these two angles we are able to implement a variety of control laws as described below. <br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> &lt;br&gt;<br /> <br /> ==Control Method==<br /> <br /> ===Closed Loop Control===<br /> [[Image:Rotary_Encoder_TR_36|thumb|right|200px|Laser Rotary Encoder]]<br /> We first attempted to control the DC motor using feedback from a [http://www.usa.canon.com/html/industrial_encoders/lre_tr36.html rotary encoder] placed directly over each magnet. From this encoder, using both the A and B channels, we are able to determine the sign of the top link's velocity. We then implemented a simple control law in which the motor is full on in the same direction that the top link is rotating. This causes the lower link to pump in phase with the top link, mimicking the motion of a person on a swing set.<br /> <br /> With this control law we were able to pump energy into the system, however, we were never able to add enough energy to get the bottom magnet to a height equal to or above the top magnet. Starting from a resting position, with the lower link dangling straight down, the bottom link pumps in phase with the top link. The bottom magnet gradually gets higher and higher, but seems to stop increasing when it reaches a height slightly below the fixed magnet. Friction seems to be the main reason why the robot can not climb.<br /> <br /> We also implemented a control law where the lower link pumped out of phase with the top link. This caused a large increase in the movement of the top link, however, the bottom magnet stays in nearly the same position throughout.<br /> <br /> &lt;br&gt;<br /> &lt;br&gt;<br /> <br /> ===Open Loop Control===<br /> Our second approach was an open loop, time based algorithm. It involves no feedback and is just a simple set of commands implemented by the PIC. In order for the monkeybot to climb, the first link must be started with some potential energy. The magnets are both on and at the same height when the algorithm begins. The algorithm is as follows, it can be tuned by changing the values A,B,C,D which are on the order of 500-600 milliseconds.<br /> <br /> Release magnet one<br /> Motor on counterclockwise for A milliseconds<br /> Motor off<br /> Magnet one on<br /> Release magnet two<br /> Motor on counterclockwise for B milliseconds<br /> Motor off<br /> Magnet two on<br /> Release magnet two<br /> Motor on clockwise for C milliseconds<br /> Motor off<br /> Magnet two on<br /> Release magnet one<br /> Motor on clockwise for D milliseconds<br /> Motor off<br /> Magnet one on<br /> <br /> This process is repeated, and overtime, the monkeybot climbs. A video of this can be found [http://www.youtube.com/watch?v=TA2VcH_GDJ0 here.]<br /> <br /> ==Mechanical Design==<br /> ===Parts List===<br /> The robot contains:<br /> <br /> Two acrylic links<br /> Two rotational ball-bearings<br /> Two electro-magnets<br /> Two rotational encoders<br /> One Pittman GM8224 DC Motor with 19.5:1 Gear Head<br /> <br /> The two links, made of 1/8” thick acrylic, create the body of the robot and create a mount for both bearings and the motor. The links were produced using a laser cutter. The rotational ball bearings mount on the links and hold the magnets, allowing the robot to swing around a fixed point. The encoders are mounted above the magnets on a bridge, so that they are capable of measuring the rotation of the link around the magnet.<br /> <br /> The Pittman motor was chosen to provide enough torque to the links to overcome friction. The gear head is also needed to get the necessary torque.<br /> <br /> ==Electrical Design==<br /> <br /> ==Code==<br /> <br /> ==Results and Reflections==</div>

NathanHenry